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Twin Whole House Rain/Tank Water + pH Treatment Filter System | Ultraviolet Sanitation to Kill Bacteria, Parasites & Viruses + pH Neutralising to Control Copper Pipe Corrosion (GT1-18-TWIN-KIT)

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Quick Overview
  • Complete Treatment System for Rain Water
  • Treats all issues with Rain Water including pH, Bacteria, Viruses
  • High Flow 50L/Min Capacity
  • Heavy Duty Stainless UV system
  • Poly Media Vessel Compliant to NSF/ANSI 44
  • Watermark Certified Filter System
  • Includes Filters/Elements and Components.
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Twin Whole House Rain/Tank Water + pH Treatment Filter System | Ultraviolet Sanitation to Kill Bacteria, Parasites & Viruses + pH Neutralising to Control Copper Pipe Corrosion (GT1-18-TWIN-KIT)

This kit has been put together to meet the demands of customers using tank water to address the issues of pH correction (remineralise the water and prevent copper pipe leaching), improved water aesthetics (clarity, tastes & odours), and the sanitation of water to kill bacteria, parasites, and viruses. The issue of acidity is of particular concern for customers with the poly/steel tank + copper pipes combo - this must be addressed in order to prevent copper pipe corrosion and pinhole leaks in your pipework later down the track (which is very costly to fix)!


Diagram of the Twin Whole House Rain Water Treatment System Installed on a Home
(Note: Tank, Pump, Weatherproof UV Enclosure, Single Socket Surge Protector & Bypass Valves not included).

Items Included In Kit

  • GT1-18C pH Neutralising Calcite Filter (Calcite Media Included) - For balancing the pH of acidic rainwater to reduce and prevent the leaching and corrosion of copper pipes.
  • GT1-9WMW Twin Filter System with your choice of filters - For clarifying the water whilst improving the taste.
  • GT7-9K Ultraviolet Sanitation System - 50L/Min Standard - For sanitising water - kills 99.9% of bacteria, parasites, and viruses.
  • GT26-4-20L HydraSil-ULTRA - For initial disinfection upon system installation to kill bacteria and fungal biofilm lurking in your pipework (treats up to 100,000L of water).

Rain Tank water will always require filtration as it isn't treated like municipal water supplies. In our experience, the most cost-effective and total solution is to use UV Sterilisation, which will ensure 99.9% eradication of all Bacteria, Parasites, and Viruses from your house water supply.

Recommended Replacement Schedule


This system is designed to handle high flow with an average household pressure pump system up to 500 kPa (72 psi), so you should not notice any significant reduction in pressure during regular water usage for an average household with a decent pump. Please note: around 344kPa (50 psi) is the ideal minimum pressure required for use with this system - pump pressures lower than 275kPa (40 psi) may cause excessive pressure drop if installed alongside a whole house filtration system (i.e. low water pressure in showers). Please note: Pump not included in kit.


This system is WaterMark Certified to Australian Plumbing Standards (AS/NZS 3497), and will need to be installed by a licensed plumber. Simply order online with free shipping to your home, and once it arrives any local licensed plumber will be able to do the installation (the system also comes with instructions)! When calling around for quotes, be sure to ask about installing a "bypass" so you can still get water into your home when the time comes for filter changes! Normally, a whole house system will be installed after the pump and before the main water line goes into your property. Your plumber will need to source fittings to install the system to your required specifications - because all setups are different, we do not supply fittings with this kit. Please refer to the description for items supplied with this kit. As the blue housing is UV resistant it can be installed in direct sunlight, however, installing the system in the shade or under cover can help prolong the life of the housings. Please note that the UV System (including the Stainless Steel Chamber + Power Supply) is not waterproof and should be protected from the weather/rain/water/moisture at all times. The UV System must also be installed directly into a single socket surge protector before being connected to a 240V 10A General Power Outlet (Power Point). It must be a surge protector - Circuit Breakers and Residual Current Devices (RCDs) are not suitable substitutes as they do not protect the unit from power surges. All aspects of this Water Filtration + UV System Kit must be protected from freezing temperatures at all times.


All Water Filtration Systems included in this package are certified to WaterMark Standards AS/NZS 3497 under Certificate number 23247. WaterMark is the standard that is required by law for a qualified plumber in Australia to install any item on municipal town water. All products used under this certification will give you peace of mind knowing that your water filter complies with Australian plumbing codes. Our WaterMark filtration systems are hand assembled here in Australia and are batch tested to ensure quality and workmanship for your filtration products.

How can you tell if a flow rate of up to 50 Litres Per Minute of water flow is suitable for your needs? Please see the below infographic:

If you have any questions at all regarding the compatibility, installation, items included with each kit, or the added extras, please contact us prior to purchasing.


Whole House Calcite Water Filter | Adjust pH from Acidic to Neutral | 52" x 12" (GT1-18C)

Suitable for tank water with a pH below 7 to help protect your plumbing fixtures/copper pipework from corrosion and degradation. Please contact us prior to ordering to ensure that you are getting the correct system for your requirements. 

Kit Includes:

  • 1x Media Vessel
  • 1x Runxin 1" Multiport Backwash Valve & Lateral Drop Tube
  • 1x 20kg Bag Filter Sand/Gravel
  • 4x 20kg Bags Calcite Filter Media
  • Instruction/Warranty Sheet

Specifications & Technical Data:

  • Vessel Size: 52" x 12"
  • Polyethylene Inner Shell
  • Max Pressure: 150 PSI (10.5 Bar)
  • Max Temperature: 50 C (122 F)
  • Min Temperature: 1 C (34 F)
  • Max Vacuum: 140mmHg (5.5" Hg) Negative Pressure (Do NOT exceed Specifications)
  • Vessel approved for water filtration use only. All other applications must be approved by the manufacturer.
  • Do not use for pneumatic or Hydro-pneumatic application.
  • Vessel must NOT be exposed to temperatures lower than -30 Degrees Celcius.
  • This Vessel complies with all requirements of P.E.D 97/23/EC Directive.
  • This water pressure vessel is tested & compliant to NSF/ANSI Standard 44 for Material and Structual Requirements Only.

Required for Installation - Add to Cart or Supply Your Own:

GT15-1 1" Spring Loaded Check Valve (Prevents Backflow)

This media vessel will require a 1-way valve (check valve) installed behind it to avoid negative pressure in the system caused by a sudden backflow of water. It is also recommended that you include an isolation valve for easy maintenance when re-filling the vessel.

GT36-83N - Neoprene UV-Resistant FRP Tank Cover (Recommended)

Constructed with UV-resistant neoprene, this tank cover ensures optimal performance even in the most demanding environments. Whether you need protection against sunlight, extreme temperatures, or other exposure, this cover has got you covered. It effectively shields your tanks from harmful UV rays, preventing degradation and extending their lifespan.

Optional Add-On - Media Funnel:

The specially-designed Media Funnel helps you fill the vessel without spilling expensive media, or getting the media stuck inside the drop tube! Use this funnel to save yourself from the hassle of having to try and push the drop tube back down into the dense media (because you've accidentally dropped media inside the tube, and had to pull the tube out to empty it)!

Why do you need a calcite filter for rainwater?

The issue of tank water acidity is of particular concern for customers with the poly/steel tank + copper pipes combo - this must be addressed in order to prevent copper pipe corrosion and pinhole leaks in your pipework later down the track (which is very costly to fix)! 

Rain water is commonly known to be in a very acidic state (around a pH of 5) naturally, and it is only when it comes into contact with earth or other organic material that the pH rises to neutral and even alkaline levels. However when you have clean gutters and a new clean poly tank (or a poly-lined steel tank), there is no organic or inorganic matter to dissolve into the water to raise the pH, thus you are left with highly acidic water sitting in your tank. This can cause extensive health issues in the long term, but it may also affect your plumbing work throughout your house. Copper is easily corroded by acidic water - if this is happening in your home, you will notice a blue/green tinge which is a signal that copper is dissolving into your water. Acidic water works its way from the inside out and if left long enough untreated, may cause your entire copper pipework to fail and need replacing.

Have you checked for signs of copper pipe corrosion in your home? Above are some examples of copper pipe corrosion, which is easily detected by the presence of blue-green staining around drains, fixtures and faucets. In the worst-case scenario, copper pipe corrosion will start with pinhole leaks, progress to multiple holes, and will eventually require you to replace the entirety of the copper pipework of your home!

This brings us to the solution to acidic water - the Calcite Filter. The GT1-18 Calcite Vessel filter features two stages of filtration:

  1. Stage 1: Filter Gravel - Gravel acts as a sand filter, filtering out dirt, sediment, and other particulates in the water.
  2. Stage 2: Calcite Marble - The way Calcite Marble filtration works, is by dissolving traces of calcium into the water to help buffer the pH back to neutral. The Calcite Marble supplied with this system is of the highest quality available in Australia, providing a consistent pH buffer and a long filtering life. On average you will need to refill about 1/2 to 1 bag full of Calcite Marble per year (which depends on water usage + pH of incoming water). We recommend that you buy a few spare bags of Calcite Marble with your order so you have it on hand for when you need to top up the calcite filter.

The drop tube is pre-cut to length and fits snugly in the centre hole of the vessel (there is a port at the bottom of the vessel that the drop tube will sit in snugly). There will be no need to cut the drop tube. The system is also fitted with a Manual Multi-Port Valve for easy and efficient backwashing of the system, again, saving you time and effort in maintaining the system.

Do I need Magnesium pH Booster Filter Media?

Please contact us prior to ordering pH Booster Filter Media. This will ensure that you are receiving the correct product for your intended purpose.

If you are considering a Calcite Vessel as part of your tank filtration set up AND the pH of your tank water is below pH. 5, you may need to add pH Booster Filter Media (Magnesium) to get the correct final pH. Adding pH Booster Filter Media to water with a pH below 5 alters the water chemistry to enable the uptake of Calcite (Calcium). For this intended use you will see the pH range anywhere from ph. 7-8 or higher depending on the pH of the incoming water. Note: when using magnesium as a pH booster, the pH will likely be above 8 when the media is new and will gradually lower over time. We recommend that you buy a spare bag of Magnesium pH Booster with your order so you have it on hand for when you need to top up the filter.

Please note that magnesium can leave a slight residual metallic taste in the water. This taste is easily removed by carbon post-filtration (included in this kit) which will produce clean, sweet-tasting water.

Using Magnesium & Calcite Together + Maintenance/Refill Instructions

Calcite and Magnesium are two common types of filter media used for pH adjustments in Rain or Bore Water. These types of media will slowly dissolve into the water over time which will mean that they require replenishment to maintain high flow rate capacity.

  • When first using a pH filter media, follow the same backwash and rinse cycles as mentioned in the system instruction manual.
  • In cases where Magnesium and Calcite are used together, add the calcite to the vessel first, then add the Magnesium on top. Ensure that you do not overfill the vessel.
    • If the pH is around 5, fill the vessel with a ratio of 80kg (4x 20kg boxes) of Calcite to 7.5kg (approx. 1/3 bag) of Magnesium.
    • If the pH is around 4.5, fill the vessel with a ratio of 71.25kg Calcite to 10-12kg (approx. 1/2 bag) of Magnesium.
  • Test your pH ongoing and add more filter media when the pH drops below the minimum desired level (ie. 6.8 pH).


WaterMark Certified Twin Whole House Water Filter System 20" x 4.5" Big Blue (GT1-9WM)

Twin Whole House Water Filter System | 20" x 4.5" Big Blue | WaterMark Certified (GT1-9WM)

The Twin 20" x 4.5" Whole House Filtration System houses a Sediment cartridge for improved water clarity and protection against particulate matter damage within the UV System, and a Coconut Carbon cartridge to reduce tastes/odours, and impart a subtly-sweet flavour into the filtered water. 

Kit Includes:

  • Twin Whole House Filter System (Pre-Installed Bracket)
  • Opening Spanner
  • 2x 1/4" Pressure Gauge Hole Plugs
  • Instruction/Warranty Sheet
  • Your Choice Of Filters (Additional Charges Apply)

Specifications & Technical Data:

  • Dimensions:
    • Height: 70cm
    • Width: 41cm
    • Depth: 20cm
  • Filter Cartridge Size: 20" x 4.5"
  • Ports: 1" Female BSP Inlet/Outlet Ports
  • Pressure: 0 - 620 kPa
  • Limit Pressure: ≤ 500 kPa
  • Temperature: 0.5°C - 37.8°C
  • Max Flow: 60 Ltrs/min (*System tested to 160 Ltrs/min. Maximum flow measured without cartridge. Refer to cartridge specs for flow rates.)
  • Initial ΔP @ Flow: 10 kPa @ 57 Ltrs/min


  • FILTER SIZE - The 20" x 4.5" size of system enables the maximum surface area and contact time for sediment, chemical, taste and odour reduction, and the best possible flow rate to prevent water pressure problems (which can occur by selecting too small a system).
    Twigs, leaves, sand, and dirt can be easily collected by a pleated filter, whilst ultra-fine particles (i.e. particles that are smaller than 100 micron, the width of a human hair) such as silt can clog up your carbon filter much quicker than anticipated and reduce your water pressure. If you have a lot of sediment in your tank, please consider whether a Triple Whole House Filter System with a Dual Sediment Pre-Filter Carbon set-up is more suitable for your water conditions.
    You may also wish to opt for a set of pressure gauges (especially if you have a lot of sediment in your tank) to help determine how clogged your filters are, and monitor the performance of your system. Simply mark the level of pressure on the gauge upon installation or when you install a new set of filters - reduced pressure over time indicates filter blockage. 

  • FILTER CHANGES AND MAINTENANCE - Lastly, we recommended filter changes on an annual basis, and offer a 12-monthly filter reminder email service to help you remember! Simply email info@filtersystemsaustralia.com.au when you place your order, and ask us to set you up with a filter reminder! Filter changes are easy enough – simply turn off the water going into the system, press down on the pressure relief valves, unscrew the sumps, replace the filters, screw it back up and turn the water back on! You may notice the water feels a bit "slippery" at first after installing new filters, but don't worry - this is normal and will go away quickly once enough water has run through the new filters. Also, if the water looks cloudy at first, again - don't stress! This is dissolved oxygen and it will go away quickly once enough water has run through the new filters.

Filter Options

Customise your filter system set up to suit your unique needs. Please read the below for a full breakdown of which filters to choose, and why*.

*Please note - the below recommendations are general information only and may not always suit your requirements. Please call us on 07 5597 4585 prior to purchase if you have any questions about your requirements.

Sediment Filters

  • Choose from pleated (washable) or polyspun (disposable) sediment filters. 
  • 5 Micron is well suited for mains/town treated water and high-quality tank/bore** water.
  • If you get a lot of sediment (typically on tank/bore**), consider upgrading to a Triple Whole House UV Sterilisation System which allows you to place a pleated filter first, followed by a poly spun with a final carbon element. 

Tank and bore** water are often contaminated with sticks, leaves, and rock sediment. In some cases, finely dissolved matter can even cause visible discolouration, build-up and staining, along with a foul taste and odour - and even a gritty texture in some rare cases! Installing a sediment filter also helps protect your pipes and carbon filters from getting blocked up with ultra-fine silt, whilst also preventing damage to the glass internals of the UV system.


Pleated (Washable/Reusable) Sediment Filters

  • Larger Surface Area Catches More Debris
  • Reusable/Washable
  • Ideal Pre-Filter for Tanks/Bores**

Pleated filters carry a much larger surface area than polyspun filters, and therefore they are able to catch a lot more debris. Simply remove the filter, clean, and re-use! Very popular for tank water when you have a lot of debris like leaves and dirt, particularly after a fresh rain. Pleated filters are also useful for bore water when you have a small amount of iron or manganese present, as pleated filters are easy and quick to clean. The washable pleats on this filter are designed to be washed and reinstalled. However, please consider that if this is drinking water you need to be careful not to overuse a pleated filter, because it will eventually gather bacterial contaminants and incur micro-tears. If the water isn't all that bad you might want to consider using a polyspun disposable filter and replace it when dirty. 

Pleated Filter Options:

  • 5 Micron Pleated Washable Sediment Filter Cartridge

Poly Spun (Polypropylene) Disposable Sediment Filters

  • High Flow & Low Pressure Drop
  • Cost-Effective & Disposable

Poly Spun filters produce a high flow and low pressure drop, and do not accumulate bacteria as much as other materials. They are highly cost-effective and disposable. All of our poly spun filters are made of 100% Virgin Polypropylene. Polyspun filters are manufactured to create a gradient density that allows for excellent sediment-holding capacity and filtration efficiency.

Polyspun Filter Options:

  • 5 Micron Polyspun Sediment Filter Cartridge


Pure Brand 100% Coconut Carbon Filters

  • High Quality, 100% Coconut Shell Carbon that Produces "Sweet" Tasting Water
  • Excellent Contaminant Reduction Capacity for Common Chemical Health & Aesthetic issues such as Chlorine, Trihalomethanes, Volatile Organic Compounds, Pesticides, Herbicides, Tastes & Odours.
  • Recommended 12 Month Lifespan if (used on Municipal Treated Water - you may get less if used on particularly dirty/turbid/raw water).
  • Designed for Minimum Impact on Water Pressure

The perfect carbon block filter is made from 100% Coconut Shell Carbon, which creates what many believe to be the sweetest tasting water. The unique pore structure of this carbon is well suited for chemical absorption, including VOC's, while reducing chlorine and chemicals that contribute to taste and odour. Coconut Carbon provides a much higher volume of micropores than coal, wood, or lignite-based carbon, thus, resulting in a more effective removal of chemical contaminants such as trihalomethanes (THMs) in Chlorinated sources. The larger surface area provides a more effective method of filtering common contaminants such as chlorine, tastes and odour molecules. The unique raw material of the coconut shell and the carbon manufacturing process ensures exceptional hardness and low ash content.

Pure Brand's 100% Coconut Carbon Block Filters are made from a combination of high-performance coconut shell carbon, unique binders, and industry-leading manufacturing processes to deliver supreme-quality filtration. Expertly designed and manufactured, these filters deliver exceptionally low-pressure drop, resistance to sediment build-up, and excellent contaminant-reduction capabilities. Pure Carbon Blocks are registered in compliance with NSF/ANSI 42, 53, and 61 for several things, including VOCs, THMs, Lead & Heavy Metal Reduction, Chloramine Reduction & Chlorine Taste & Odour reduction. This also includes meeting incredibly high standards of purity and safety in the materials used.

Please see below for a full comparison of our range of Carbon Filters:

GT4-19CTO - 5 Micron Chlorine Taste & Odour Reduction Coconut Carbon (Budget Option for Improved Chlorine Taste & Odour Reduction in Tank Water)

  • CTO Carbon is our standard recommendation for chlorine reduction, improved sweet taste and reduced odour - great value and quality!

Chlorine is generally the biggest concern for those on municipal water or those who use chlorine to disinfect their tanks, due to the offensive chemical smell and taste it produces, along with potential health effects resulting from topical exposure or consumption. Whilst Chlorine is effective at sanitising bacteria and viruses, Volatile Organic Compounds and Disinfection By-Products such as Trihalomethanes (THM) and Chloroform can form when chlorine reacts with oxygen and other chemicals in solution. The Chlorine, Taste, and Odour cartridge will provide you with clean, great-tasting water free from nasty chemicals and remove or reduce any chemical smells in the water caused by free chlorine.

Bore/Tank Water** Filter Combo Example*:

Filter 1: 5 Micron Pleated OR 5 Micron Poly Spun Sediment Filter
Filter 2: 5 Micron CTO Carbon 
Filter 3: Ultraviolet Treatment


GT4-19BCC - 5 Micron Bacteriostatic (Silver Impregnated) Coconut Carbon Block (For Preventing Filter Biofouling in Raw/Tank/Bore** Water)

  • Ideal for Pre-Filtering tank** & Raw Water Prior to Ultraviolet Treatment.
  • Prevents Bacteria from Proliferating within the Cartridge.
It's important to note that Silver Impregnated Carbon is BACTERIOSTATIC - meaning that it inhibits or prevents the increase or growth of bacterial levels WITHIN the filter only. Silver Impregnated/Bacteriostatic Filters DO NOT sanitise, disinfect or remove bacteria from water. If this is your goal, further treatment is required - please refer to the note at the bottom of this page **FILTERING TANK AND BORE WATER - IMPORTANT INFORMATION BEFORE YOU ORDER**.
Contrary to popular belief, carbon does not filter out bacteria. Whilst carbon effectively removes odours and taste issues from water, carbon ash is actually a source of nourishment for bacteria, making wet carbon filters a breeding ground for microbial contamination (Note: this should not be an issue on mains water as Chlorination is designed to kill bacteria). This, unfortunately, causes biofouling of the filter cartridge which can lead to premature blockage (costing you hundreds of dollars to replace cartridges more frequently than you should have to), putrid tastes and odours and worse - illness as a result of ingesting the bacteria that has passed through the cartridge and into your drinking water! Using a rotten filter can make you seriously sick - so if in doubt - chuck it out!
Silver Impregnated Carbon, on the other hand, is bacteriostatic - meaning that it is proven to inhibit the growth of carbon-fed bacteria within the filter to prevent bio-fouling and prolong the life of a cartridge - even while it is not being used! Therefore, when it comes to filtering raw water, Bacteriostatic (Silver Impregnated) Coconut Carbon is the number one choice, as this media is specifically designed for use with rainwater, tanks and bores* to prevent bacteria from breeding and colonising within the carbon and extending the life of your filter. Silver Impregnated Carbon is ideal for periods of time where the filter may go unused. If you want to get the most out of your carbon filter, you can even go one step further and dry it out between uses! 

So, how does Silver Impregnation inhibit the growth of bacteria in a carbon filter? When bacteria come into contact with silver, the silver ions puncture the bacteria's cell membrane and wreak havoc by binding to and denaturing the bacteria's DNA. The sulphydryl group already within the bacterial cell also reacts with the silver, producing a silver sulphur complex that immobilises the respiratory and reproductive activity of the bacterial cell. Interestingly, Silver Impregnation has an incredibly long-lasting effect, as the dead bacteria then leach the silver molecules back into their environment, effectively killing neighbouring live bacteria as they die.

Dead bacteria store the microscopic silver particles within their cells (see above image of dead bacteria with silver nanoparticles (white spots)), making them deadly to live bacteria.
(Source: "Antibacterial Activity of Silver-Killed Bacteria: The "Zombie" Effect" (2015), https://pubmed.ncbi.nlm.nih.gov/25906433/).


Tank Water/BoreWater** Filter Combo Example* (Only Recommended Over 50 psi/344 kPa Pump Pressure):

Filter 1: 5 Micron Pleated OR 5 Micron Poly Spun Sediment Filter
Filter 3: 0.5 Micron Silver Impregnated Carbon
Filter 3: Ultraviolet Treatment


Bore/Tank Water** Filter Combo Example*:

Filter 1: 5 Micron Pleated OR 5 Micron Poly Spun Sediment Filter
Filter 2: 5 Micron Silver Impregnated Carbon 
Filter 3: Ultraviolet Treatment


GT4-19LRC - 0.5 Micron Lead Reduction Composite Coconut Carbon (For Chlorine Reduction & Heavy Metal Concerns in Rainwater, Old Infrastructure, Cities & Industrial Areas)

  • Reduction of Chlorine, Tastes, Odours and Heavy Metals.
  • Ideal for Filtering Tank/Bore Water where atmospheric pollution may be of concern.

On the basis of local and atmospheric contamination, it is not uncommon to have elevated heavy metal levels in rainwater supplies. 

Constant exposure to heavy metals combined with the different chemicals being used to treat our water supplies can have serious health effects, and can also cause severe plumbing problems within our homes. Rainwater (acidic pH) and chlorine/chloramine treated water (basic pH) both tend to be quite corrosive, and this can wreak havoc on the internal plumbing and fixtures within old municipalities and even the copper and brass fixtures in your home (which fittings may contain traces of lead)! The chemical quality of rainwater can also be negatively impacted for those living near heavy industry or in areas with heavy traffic emissions. For example, rainwater samples in Port Pirie, South Australia, (which has one of the world’s largest lead smelters), have been found to contain levels of heavy metals such as lead that exceed Australian Drinking Water Guidelines by up to ten times! (Even bushfire can contaminate rainwater, in which case you'll need to have your tanks cleaned out!)

This cartridge is perfectly suited to reducing trace heavy metals that may be present in your water. The technologically-advanced Lead Reduction Cartridge is impregnated with BASF ATS Lead and Heavy Metals Adsorbent Media, which features a high capacity for the reduction of Lead and other heavy metals such as Arsenic, Chrome, Copper etc., along with the usual benefits of carbon in the reduction of Chlorine, Volatile Organic Compounds, and Trihalomethanes.

Tank Water/BoreWater** Filter Combo Example* (Only Recommended Over 50 psi/344 kPa Pump Pressure):

Filter 1: 5 Micron Pleated OR 5 Micron Poly Spun Sediment Filter
Filter 2: 0.5 Micron Lead Reduction Carbon Block 
Filter 3: Ultraviolet Treatment


GT4-19SMC - 0.5 Micron Surface Modification Coconut Carbon (For Reducing Water Discolouration/Tannin Reduction)

  • Ideal for Reducing Tannin Discolouration, Chlorine, Tastes & Odours in Tank** & Raw Water.

Surface Modification Carbon uses a unique blend of highly reactive catalytic coconut carbon with the highest performance reduction technology. SMC filters are the best type of cartridges to reduce water discolouration, including rust and most tannins. Surface Modification Filters are commonly referred to as ‘Tannin Removal Filters’. Also filters Chlorine. 

A Note on Treating Tannin:
Tannin removal can be a bit hit and miss - usually carbon will remove most of the tannin, but sometimes it doesn’t. Because of this, we normally recommend doing a small scale “litmus test” with a cheap carbon filter to see if this makes a difference to the colour. If it works, then we can be more certain that you will get a good result with a standard carbon filter, and a great result with this 0.5 Micron SMC Tannin Reduction filter! Please contact us before purchasing this filter if you are unsure about the source of colour in your water, so that we can help you with the right recommendation to get the best result!

Tannin Reduction Filter Combo Example* (For Tank/Bore**) (Recommended Over 50 psi/344 kPa Pump Pressure):

Filter 1: 5 Micron Pleated OR 5 Micron Poly Spun Sediment Filter
Filter 2: 0.5 Micron Tannin Reduction Carbon Block 
Filter 3: Ultraviolet Treatment


Watermark Ultraviolet Water Sterilisation System | Whole House 50 Litre Per Minute UV with 316 Stainless Steel Chamber (GT7-9K)

Raw rainwater is full of bacteria, parasites, and viruses! Treat it with UV Sanitation - a safe, highly effective, chemical-free and low-maintenance alternative to Chlorine!

Kit Includes:

  • GT7-9K - WaterMark Whole House UV System 40W | 1” Ports
  • GT7-8-BRK (x2) - 1 Pair of Aluminium Mounting Clamps + Screws
  • GT7-9K-Lamp - 840mm 4 Pin 40W UV Lamp
  • GT7-9K-Thimble - 895mm Quartz Thimble 23mm*OD
  • GT7-9K-PS - UL Certified Ballast 40W Australian Plug + Earth Cable
  • GT7-2N-OR - NSF/ANSI 42 Compliant O-Rings Suit 23mm*OD

Specifications & Technical Data:

  • Commercial Grade Electropolished 316 Stainless Steel Chamber
  • Visual & Audible Lamp Failure Alarm
  • 1” BSP Threaded Male Port Connections
  • Strong Aluminium Mounting Brackets – Surrounds Chamber
  • Max Flow - 50L/Min (For 30mJ/cm² EOL)
  • High Intensity UV Lamp – Up to 50L/min @ 30mJ/cm²
  • Lamp Power - 40W
  • Voltage - 230-240V
  • Max Pressure - 125 psi
  • Working Pressure - Up To 70psi
  • Dimensions
    • Length - 900mm (Without Plug)
    • Between Ports - 780mm

Whilst many people enjoy the sweet taste of rainwater, we cannot stress enough that drinking raw, untreated water from a tank is a very bad idea! Scarily, in Australia the general public perception is that rainwater is pure, clean, and safe to drink - but according to the Australian Environmental Health committee’s Guidance of the Use of Rainwater tanks, the fact is that the microbial quality of tank-collected rainwater is typically WORSE than regular urban tap water!

Raw, untreated water contains a microbiologically sickening soup of bacteria, viruses & parasites that inevitably make their way into your tank from disease-spreading insects such as blood-sucking mosquitoes, the excrement and decaying carcasses of frogs, snakes, rodents, and possums that commonly live in and around tanks, and the droppings from bats and birds flying overhead! Also consider that bacteria tend to proliferate in moist and warm environments - meaning that warmer weather, in particular, has the tendency to turn your tank into a putrified bacterial breeding ground. E.Coli, Salmonella, Legionella & P. Aeruginosa are some of the more common pathogenic bacteria found in rainwater tanks, whilst Cryptosporidium and Giardia Cysts are the most common rainwater tank parasites. All of these pathogens are a common cause of Gastro!

What Are the Symptoms of Cryptosporidiosis?Giardiasis : Symptoms, causes, complications, & remedies | FactDr

Cryptosporidiosis & Giardiasis are common causes of gastro illness in humans and animals!
(Image Sources: Shutterstock.com)

Thus, whilst rainwater may smell odourless, taste great, and look clean and clear to the naked eye, with the human senses alone, you simply cannot tell what potentially harmful microscopic contaminants could be lurking in your tank water (even after filtering the water with carbon) – and you certainly don’t want to be drinking it!

UV Water Sanitation is by far the most important filtration process when it comes to rainwater treatment. Ultraviolet sanitation works by breaking down the cell wall of micro-organisms (bacteria, parasites, viruses, fungi & yeast), allowing oxidation to occur which in turn prevents the microbe from multiplying until it is finally eradicated. Ultraviolet filtration is a chemical-free solution to water sanitation, creating no by-products in the water, and is recommended by the Australian Drinking Water Guidelines as a safe, effective and chemical-free water disinfection technique:

A comparison of Drinking Water Disinfection Methods approved for use in Australia under the Australian Drinking Water Guidelines (Version 3.7, 2022))
(Source: NRMMC (2011) Australian Drinking Water Guidelines Paper 6 National Water Quality Management Strategy. National Health and Medical Research Council, National Resource Management Ministerial Council, Commonwealth of Australia, Canberra, pp. 214.)

How can you tell if a 50 Litres Per Minute UV System is suitable for your needs? Please see the below infographic:

Water Pre-Treatment Specifications

  • Hardness < 120 mg/L
  • Turbidity < 1.0 NTU
  • Iron < 0.3 mg/L
  • Manganese < 0.05 mg/L
  • Tannins < 0.1 mg/L 
  • Filtration < 5uM Particulate Filtration

Installation Requirements

  • This appliance must be installed directly into a single socket surge protector before being connected to a 240V 10A General Power Outlet (Power Point). It must be a surge protector - Circuit Breakers and Residual Current Devices (RCDs) are not suitable substitutes as they do not protect the unit from power surges.
  • The GT7-9K UV System is not weatherproof and all components (including the chamber and electronics) must be shielded from direct sunlight and weather extremes such as rain, storms, and frost. Looking for a fully enclosed Whole House UV System?  Check out the specially designed High Performance | Weatherproof Twin Filter + UV Whole House Water Sanitation System (HPF-UV):

UV System Maintenence Notes:

Ultraviolet systems are rated based on a dosage level of UV-C radiation into the water (mJ/cm²), with 30mJ/cm² being the standard level of disinfection and a minimum dose of 40mJ/cm² required to comply with the Australian Drinking Water Guidelines. Our lamps are rated with a 9000 hour (1 year) lifespan, after which point the lamp will naturally degrade and the level of radiation produced by the lamp cannot be guaranteed.

The UV lamp sits inside a quartz thimble, which protects the electrical components of the lamp from making contact with the water. We specifically use quartz (fused silica) for this application because it is strong, exhibits thermal resistance, and has excellent UV transmission properties. However, over time, metal ions fused within the silica structure of the quartz thimble interfere with the UV-C radiation produced by the lamp, which reduces the UV transparency of the glass and causes it to become fragile. This process is called solarization. Tannin, bio-film, algae, and scale can also build up on the outside of the glass thimble, further preventing ultraviolet light produced by the lamp from penetrating through the thimble, and impairing the system's ability to sanitise the water passing through. It is recommended to clean the thimble periodically (every 3-6 months with alcohol or a mild detergent.

Thus, we recommend replacing the lamp every 12 months, and the thimble every 1-2 years.

GT7-9K UV System Replacement Parts:

HydroSil Ultra 7.5% | Silver Stabilised Hydrogen Peroxide Water Sanitiser | 20 Litres

As UV is a point of use (non-residual) form of water sanitation, we strongly recommend dosing your tank with a product such as Hydrosil Ultra 7.5% Water Sanitiser upon installation of your Whole House UV System, to ensure full protection against bacterial and fungal contamination/biofouling/biofilm build-up in your pipework and/or filter system.

HydroSil is a food-grade silver and hydrogen-peroxide based water sanitiser, which acts to oxidise bacteria and fungi without leaving any dangerous residues behind. HydroSil sanitizes and protects your tanks and filtration devices to help make your tank water safe for human consumption. HydroSil is not a chlorine-based chemical like most sterilizers on the market today. It is non-toxic, and safe to use around your home and family.

Dosage Instructions for the Initial Treatment Immediately Prior to System Installation:

  • HydroSil should be dosed at a rate of 200mL (2L) per 1000L (10KL) of tank water.
  • Turn on every tap in the house until you are satisfied that the treated water has passed through.
  • Immediately install the Whole House System.
  • It is recommended that this dosing procedure should be completed every time the UV lamp is changed.




About Bore Water

Bore water will always require filtration, as whilst you would think it is “naturally purified” to some extent as the water seeps through the aquifer via various layers of bedrock, this water is highly susceptible to contamination by bacteria, viruses, parasites (see: Brain-Eating Parasites), sewerage (think human excrement, cleaning and bathing products), chemicals, fertilisers, pesticides, minerals, heavy metals (such as lead, zinc, chromium, copper, cadmium, arsenic and nickel), and sometimes even radioactive elements (such as uranium) from both natural sources and human activity. As with rainwater treatment, the most cost-effective solution is typically to use 5 Micron Carbon Filtration in combination with UV Sterilisation to ensure 99.9% eradication of all parasites, bacteria, viruses. However, this system is not always a "total fix", as bore water chemistry is incredibly complex, and sometimes may not even be treatable. Yet another common misconception we often encounter is that carbon can filter out anything and everything – but unfortunately, carbon doesn’t kill bacteria or remove minerals, salts and other such dissolved inorganic substances!

We STRONGLY recommend that you get your bore water tested to determine if there are any underlying issues in the water chemistry of your bore, before you make any purchases or try to filter it. If you have not had your water tested yet and would like to get this done, please contact us to have your bore water analysed.

Twin Water Filter

Suits:Bore, Tank, Dam or Town water
Size: 20" x 4.5"
Ports:1" Ports
Max Flow:60 Ltrs/min (tested to 120 Ltrs/min)

Calcite Filter

Suits: Bore, Tank, Dam Water
Size: 52" x 12"
Ports: 1" 
Functions: Filter, Fast Rinse, Backwash
Working Range: 5.4 - 6.8 pH
(Supplementary Filter media is required for water less than 5.4 pH - Please contact us for details)

UV Filter System

Max Flow                    50L/Min (For 30mJ/cm² EOL)
Voltage                      230-240V
Chamber                    316 SS
Ports Size                   1” BSP
Max Pressure              125 psi
Working Pressure        Up To 70psi
UV Lamp                    GT7-9K-Lamp
Lamp Power               40W
Lamp Length               840mm
Thimble Length           895mm
Thimble OD                23mm
Thimble                     GT7-9K-Thimble
Ballast                       GT7-8K-PS


Length                          900mm (Without Plug)
Between Ports               780mm

Earthing: Before operating this unit, it must be earthed. Simply attach the supplied earthing cable connected to the chamber to an earthing rod.

Technical Data

UV systems are not designed to be turned on and off. Doing this may shorten your lamp life. Lamps should be changed every year. The lamp may still be working, but after 1 year, the power may not be able to kill all bacteria. The Quartz thimble should be replaced every 2 years. If hardness is high it is recommended to service and clean the UV thimble every 6 months or as required to remove and scale that may build up.

Dosage – GT7-9K

General Disinfection (Common)                 30mJ/cm²
Flow Rate Maximum (EOL)                        50L/min

Recommended for Drinking Water             40mJ/cm²
Flow Rate Maximum (EOL)                        37L/min

UV System Maintenence Notes:

Ultraviolet systems are rated based on a dosage level of UV-C radiation into the water (mJ/cm²), with 30mJ/cm² being the standard level of disinfection and a minimum dose of 40mJ/cm² required to comply with Australian Drinking Water Guidelines. Our lamps are rated with a 9000 hour (1 year) lifespan, after which point the lamp will naturally degrade and the level of radiation produced by the lamp cannot be guaranteed.

The UV lamp sits inside a quartz thimble, which protects the electrical components of the lamp from making contact with the water. We specifically use quartz (fused silica) for this application because it is strong, exhibits thermal resistance, and has excellent UV transmission properties.

However, over time, metal ions fused within the silica structure of the quartz thimble interfere with the UV-C radiation produced by the lamp, which reduces the UV transparency of the glass and causes it to become fragile. This process is called solarization.

Tannin, bio-film, algae, and scale can also build up on the outside of the glass thimble, further preventing ultraviolet light produced by the lamp from penetrating through the thimble, and impairing the system's ability to sanitize the water passing through.

Thus, we recommend replacing the lamp every 12 months, and the thimble every 1-2 years.

Return Policy

Due to the nature of the products we sell, a strict return policy is in place. We work with food grade certified materials that must be un-opened and un-used as to be able to be re-sold.

You may receive a refund or credit of equal amount, less the restocking fee if applicable and any other deductions that are relevant.

  • Wrongly purchased items may be returned for a merchandise credit, this applies for but not limited to: Wrong size, wrong system etc.
  • 30 Day return Policy: Returns will not be accepted without prior approval or after 30 days of invoice date.
  • All returns will incur a 17.5% restocking fee or cost to send the item to you whichever greater. FSA may use discretion to determine the restocking fee.
  • Any damages (minor, that can be repaired) will incur a fee which will be deducted from the total refund which will be equal to the cost of the replacement
    parts (List Price) and labour charge (if applicable) to repair the system(s). This will be separate to the restocking fee.
  • Any damage considered to be major and not feasible for repair may be refused and the return request will be void. The customer will be responsible for the return freight or disposal of the damaged unit.
  • Return shipping is to be paid by the buyer to the address provided. It is recommended that the customer applies transit warranty to the return freight in case of damage.
  • Any damages to the system that were not reported to FSA within 48 business hours of receipted delivery are not covered under our transit warranty.

  • Should the item appear faulty or doesn’t work how described, the unit/item must be returned for testing (if requested), the return postage paid by the buyer. If the unit/item is deemed to be faulty, compensation will be provided for the postage cost (Proof of cost required). If the unit/item is deemed to be in working order and as described, the buyer will responsible for return postage.

If you have any questions about our return policy, please contact us before purchase. This will also help to ensure you purchase the correct product that suits your requirements.

Other than pH testing, what warning signs do I look for if I suspect that my rain water tank is acidic?
Acidic water can have a few different warning signs. The main offender is any green or bluish staining around fixtures or discoloration in the water itself. This green residue is the copper that was once present in your plumbing (or fixture) that has been dissolved into your water due to a low pH. In some cases, some people have actually had their hair turn green due to the high levels of copper in the water. At the high end of this, people have become sick due to the levels of copper that they are drinking in their water. A pH test is highly important, especially if you have copper plumbing or fixtures.

How do I test my rain water pH?

pH test strips are the best way of determining an accurate pH. When testing this, you must ensure that your pH test strips are high range i.e. they go from at least 4-10 pH. People will commonly go to a pool shop or use pool test equipment which is handy, however the pH range is usually 6.2 and up.
It is vital that you have an accurate pH reading to determine whether or not Calcite alone is enough to treat the water. If your pH is lower than 6.2 it is highly important you treat the water to avoid damage to your plumbing and also your health.

What is the maintenance with a Calcite Filter?

The calcite filter will slowly over time introduce trace amounts of calcium into your water (5-20ppm) which is enough to elevate your pH from acidic to a neutral state.
In doing this, the filter media itself literally dissolves so will need to be topped up eventually.
To determine when you need to top up the filter, simply test your pH, if you get a reading of 7pH or more, the filter is working fine. However, if the pH drops under 6.8 pH, you will require a top up of calcite into the filter. Usually an average house will go through anywhere between half, to 1 ½ bags of calcite per 12 months, obviously this can vary due to water usage and pH. When you top up the calcite filter, you will need to give it a quick backwash to remove any calcite dust. Flush the filter until the water runs clear then the filter is ready for use.

Do I require any other filtration in conjunction with a calcite filter?

As the calcite filter already includes a manual backwash head, you will not require a sediment filter after it as you can wash the filter until the water runs clear. However, if you are on tank water, we strongly advise that you have standard filtration accompanied with Ultraviolet Sanitation. All tank water should be filtered.

Is everything supplied with the system, or do I need to purchase anything extra?

The Calcite Filter is supplied with filter gravel, and Calcite marble for the filtration. Usually a plumber will conduct the installation, in which case the plumber should supply any additional fittings or pipe needed for your specific installation.
There is 1 Key item you will need to ensure is purchased/installed.
1. One-way Check Valve (Non Return Valve): This is to ensure that no back flow occurs in the event that the water somehow vacuums backwards through the vessel. If this occurs, there may be enough negative pressure to cave in the filter vessel.

Will a Calcite Filter work on pH lower than 6?

Calcite filter media has an effective pH range between 5.2 and 6.8 pH. This pH range is the most common that you will find in domestic tank water.
However if you have very clean tanks and gutters, you may have a pH that is below 5.2 in which case Calcite on its own will not work. The solution to this is to use a Magnesium Oxide media which dissolves in all acidic pH ranges, giving the pH a “Jump Start” so that the calcite can take over. This is the same media we use in our “High Alkaline” Water filters.


What is the recommended dosage rate of HydroSil-ULTRA for different applications?

As an initial treatment for bacteria and viruses you will need 200mL / 1000L. To put that into perspective for rain water tanks.
1L HydroSil-ULTRA = 5000L Water
5L HydroSil-ULTRA = 25,000L Water
20L HydroSil-ULTRA = 100,000L Water
This dosage rate will give the tank a high initial dosage to saturate the tank and oxygenate the water. It is enough to kill 99.99% of harmful bacteria and viruses in the water.
HydroSil-ULTRA will remain in the water as a residual for a period of 30-90 Days (depending on the water quality). Once the residual clears, it is time to re-dose the tank at ½” the initial rate (i.e. 100mL / 1000L) to ensure that your water tank stays oxygenated and free from harmful bacteria and viruses.

Can I test the water accurately to know when I need to re-dose?

We have Peroxide Test Strips in stock that accurately measure the concentration of peroxide (ppm) in the water. As a general rule, once there is no colour change in the strips (<0.5 ppm) you are due to re-dose the tank at 100mL / 1000L.

There are similar products on the market that recommend a much lower dosage rate compared to HydroSil-ULTRA, why is this?

Other Hydrogen Peroxide sanitisers (7.8%) on the market recommend a lower dosage rate mainly due to cost. Silver Stabilised Hydrogen Peroxide is a fairly expensive compound to manufacture correctly and requires the highest quality materials and base ingredients. Due to the expense of the product, to make it more attractive to customers, a lower dosage is recommended to lessen the expense to the customer. In reality, this can be dangerous as you may not be protected from harmful bacteria which require a minimum dosage of 100mL/1000L. As we are the Australian Distributor for HydroSil-ULTRA, we have a much more affordable price to offer to the consumer to keep costs down without endangering customers due to under dosage.

Will HydroSil-ULTRA Kill Giardia?

Giardia is a serious issue in tank water and is something that needs to be addressed urgently, especially for the elderly or young children.
To kill Giardia using HydroSil-ULTRA you will require a concentrated dosage of 400mL/1000L of water (double the recommended dosage). As Giardia is not a bacteria or virus (it’s a parasite) it takes longer for the peroxide to penetrate the protective outer layer. Once the layer is breached the parasite will die in the oxygenated water. Ideally, we recommend that you

How do I know what size UV system I need?
Ultraviolet Sanitation Systems are commonly graded based on a pre-requisite water assessment (TDS, Turbidity and Pre-Filtration), and a Peak Flow Rate. There are 4 Main types of UV Systems for domestic use. Firstly, there is Undersink or Drinking Water applications; These systems tend to be quite compact which is convenient due to space requirements. The flow rate on these systems range from 3-6L per minute which is suitable for use with a Drinking Water Faucet Tap. Next, you have the Small Home or Caravan/Granny Flat Size UV which is capable of up to 30L/Min (Or 2-3 Outlets running simultaneously). While this sized system is a great way to help budget your water filtration & Sanitation, you need to ensure that your flow rate does not exceed 30L/Min. The most common UV system you will come across is the Whole House Water Sanitation System which utilises a 40W globe to run up to 50L/Min. This system is enough to cover most domestic applications on houses with 2 bathrooms and kitchen. When a more commercial type application is needed, say for a block of Cabins or multiple houses, a Semi-Commercial Sanitation Unit Is required to achieve the peak flow rate between 90 and 200L/Min.

Does UV require Power to run?
Yes, the UV systems will require standard Australian 240V power supply to run. The ballast is a multi-level unit capable of powering systems from 10W up to 40W. It is recommended to leave the UV running at all times, when the UV light is turned off repeatedly, the life of the lamp may be reduced and rendered ineffective. It is also required that the UV is connected to the power via a surge protector.

What is the UV Filter made from?
Our UV systems are made from Industrial Grade, Certified 316 Stainless Steel. Many Australian suppliers elect for the cheaper 304 grade to minimise their cost, and still charge a premium price.

Does the UV system require servicing and is it DIY?
The UV lamp itself has an effective lamp life of 12 months or 9000 Hours. Replacing the lamp is a few simple steps: Firstly, turn off the power. Remove the rubber boot and slide out the UV tube, replace with the new tube, re-insert into the UV system then turn the power back on. Ensure that the lamp does fire correctly then the system is ready for service once more. The Quartz Thimble which encases the UV lamp and seals the water does require servicing also. We recommend that a licenced plumber conducts this as it involved un-installing the glass thimble. Over time, you may get Scale & Sediment build up on the quarts which can inhibit the effectiveness of the UV lamp. Clean this thimble using mentholated spirits and a new microfiber cloth, then rinse with water. NOTE: try not to get water inside the tube during this process. The UV Thimble is recommended to be replaced every 2 Years.

Does the UV system go BEFORE or AFTER standard filtration?
The UV system must be installed AFTER standard filtration. This helps to ensure that the prerequisite water parameters are met for the UV lamp to work effectively.

Is there anything else I need to do when installing a UV water filter for Whole House?
Ultraviolet Sanitation Systems will only be effective at treating the water that passes through the chamber. It is possible that there are traces of bacteria and viruses that are already present within your house and plumbing, mainly around fixtures and anywhere close to open air. We recommend as a precautionary measure to dose your water tank with HydroSil Water sanitiser and then opening up numerous taps around the house to allow the HydroSil to flow to all areas of the house, killing any residual bacteria and viruses that can be found in the house. You can then safely install your UV system, knowing full well that your water will now be 100% Bacteria and Virus Free.