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Twin Whole House Rain Water Treatment Filter System | Ultraviolet + pH Neutralising 1-18-Twin-Kit

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Full Australian WaterMark Certification

These Water Filtration Systems are certified to WaterMark Standards AS/NZS 3497 Under the 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.


This kit has been put together to meet the demands of many customers using tank water.

Tank water will always require filtration as it isn't treated like municipal water supplies. The most cost effective and total solution to do so is to use UV Sterilisation, which will ensure 100% eradication of all Bacteria and Viruses from your house water supply.

The only alternative would be to use an undersink filter for drinking water, which is effective at stopping cysts such as giardia, but won't protect you from harmful bacteria or viruses such as E-Coli which can enter the water through frogs excrement. On top of this, all other taps i.e the shower, basins and other taps wont be treated so you can still be exposed to these viruses and bacteria through other means other than ingestion.

Items Included In Kit

GT1-9WMW   Twin Filter System
GT2-28N        Poly Spun Sediment Filter 5 Micron
GT4-19CTO   Carbon Block Filter 5 Micron
GT7-8K          Ultraviolet Sanitation System 50L/Min
GT1-18G        Calcite Filter (Media Included)
GT26-4-20L    HydraSil-ULTRA - Treats Up to 100,000L Water

PLEASE NOTE: The Third photo is an example photo only, not all items included in the photo are supplied with this kit, you will only receive the items that are listed above. You will need to source your own fittings to install the system to your required specifications. Because all set ups are different, we do not supply the fittings with this kit. Please refer to description for items supplied with this kit.

The UV ballast is not waterproof and should be protected from water/moisture at all times.

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

Calcite Filter - pH Correction

Now days many people are getting brand new Poly Rain water tanks installed on their property. Rain water is commonly known to be in a very acidic state (around 5pH) 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, 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 known to be the worst affected part of your house by acidic water, you will notice a blue/green tinge to the water 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.

This brings us to the solution to acidic water, The Calcite Filter.

There are many note-worthy features that need to be addressed with this system.

The system is also fitting with a Manual Multi Port Valve for easy and efficient back washing of the system, again, saving you time and effort to maintain the system. This will also mean you do not need a second expensive post filter to catch the fine particles/dust produced by the calcite when it is first used.

The filter is made up of 2 main filter components:

Firstly: A bag of filter gravel which acts as a sand filter, filtering out dirt sediment and other particulate in the water.

Secondly: We use a High Grade Calcite Marble filter media. This calcite is the Highest Quality available in Australia. This in turn will provide much better consistency and filtering life.

The way this filter works is by dissolving traces of calcium into the water to help buffer the pH back to neutral. 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). This is done through the convenient side fill port mentioned above.

The drop tube is pre-cut to length and fits snugly in the centre hole of the vessel (there is a port in the bottom of the vessel that the drop tube will sit in snugly). There will be no need to cut the drop tube.

We recommend that you buy a few spare bags of calcite with your order so you have it on hand for when you need to top up the calcite filter.

Please contact us prior to ordering to ensure that you are getting the correct system for your requirements.

Twin Whole House Water Filter

Contains:5 micron Poly Spun Sediment Cartridge
5 micron Carbon Block Cartridge
Opening spanner

5 micron Poly Spun Cartridge:

Poly Spun is the best type of filtration you can get. They do not accumulate bacteria as much as other materials, as well as being high flow and low pressure drop. Effective in all applications. 5 micron is a reasonably fine filtration and would be suited on high quality bore water or town water or infront of RO's.
100% Virgin Polypropylene material - Compatible for Our Watermark Certified Systems
Purefer Polypropylene filters are made using a unique single nozzle manufacturing process, where a single nozzle blows melted polypropylene onto a spinning 5 micron filter core. As more Polypropylene is blown, the filter diameter gradually widens and the outer density of the filter decreases.
This unique manufacturing process gives Purefer filters a true Gradient Density that allows for a greater dirt holding capacity and higher filtration efficiency compared to standard melt blown filters made from multiple nozzle blowers.

5 micron PURE Carbon Block Cartridge:

Pure Coconut Carbon Block Filters are made from a combination of high-performance coconut shell carbon, unique binders and industry leading manufacturing processes to deliver trade quality carbon block filters. They deliver exceptionally low pressure drop while maintaining a high dirt holding capacity with excellent contaminant reduction capabilities.

Pure Carbon Blocks are registered in compliance with NSF/ANSI 42, 53 and 61 for several things, including VOC’s, THM’s, Lead & Heavy Metal Reduction, Chloramine Reduction & Chlorine Taste & Odour reduction. This also includes meeting standards of purity & safety of the materials used.

The perfect carbon block filter is made from 100% Coconut Shell Carbon, which creates what many believe to be 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


  • High chlorine, taste & odour reduction
  • Long Life
  • High Flow with Low Micron Rating
  • Sweet tasting, pure fresh water
  • No release of carbon fines
  • Removal of VOC from water supply
  • Decreases COD and BOD
  • Purification of MSG
  • Low pressure drop
  • 5 micron filtration
  • Meets the requirements of the FDA for food and beverage contact

Ultraviolet Water Sanitation System

UV Water Sanitation is by far the most important filtration process when it comes to rain water treatment. Rain water harbours bacteria of all types but is some cases much more harmful bacteria may be present in the tank. E-Coli is a common bacterium in tank water and is due mostly to Frogs in and around your tanks/catchment. Ultraviolet sanitation works by breaking down the cell wall of a micro-organism allowing oxidation to occur which in turn prevents the bacteria from multiplying until it is finally eradicated. Ultraviolet filtration is a chemical free solution to water sanitation creating no by products in the water.

​We recommend adding the optional UV Thermal Relief Valve for any situation where the UV system is installed and water is not continuously running through the system. This will prevent the UV system from overheating and damaging the seals 

Kit Contains

  • GT7-8K              WaterMark Whole House UV System 40W | 1” Ports
  • GT7-8-BRK (x2)   1 Pair of Aluminium Mounting Clamps + Screws
  • GT7-8K-Lamp     840mm 4 Pin 40W UV Lamp
  • GT7-8K-Thimble  895mm Quartz Thimble 24.5mm*OD
  • GT7-8K-PS         UL Certified Ballast 40W Australian Plug + Earth Cable
  • GT7-8N-OR     NSF/ANSI 42 Compliant O-Rings Suit 24.5mm*OD


  • Commercial Grade Electropolished 316 Stainless Steel Chamber
  • Visual & Audible Lamp Failure Alarm
  • 1” BSP Threaded Male Connections
  • Strong Aluminium Mounting Brackets – Surrounds Chamber
  • High Intensity UV Lamps – Up to 50L/min @ 30mJ/cm²

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

* Based on Average Peak Flow Rate of 5 People Living in a 4 Bedroom House incl 2 Bathrooms

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 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                    GT7-8K-Lamp
Lamp Power               40W
Lamp Length               840mm
Thimble Length           895mm
Thimble OD                24.5mm
Thimble                     GT7-8K-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 – GT7-8K

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

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

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.