4 Stage Reverse Osmosis Under Sink Premium Model 021-4p-Gm
  • 4 Stage Reverse Osmosis Under Sink Premium Model 021-4p-Gm

PSI-021-4P-GM 4 Stage Reverse Osmosis Under Sink Premium Model

This Reverse Osmosis Undersink 4 Stage model PSI-021-4P-GM is a premium low waste 1 to 1 ratio unit featuring the exclusive membrane flushing. It has the Dow Filmtec 300 litre per day TFC membrane, the 300 litres is rated at 50 psi. Optional ALKALIZE

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Optional re-mineraliser?
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This is a premium system made from the finest quality parts available without compromise.

This Reverse Osmosis Undersink 4 Stage model PSI-021-4P-GM is a premium low waste 1 to 1 ratio unit featuring the exclusive membrane flushing.

It has the Dow Filmtec 300 litre per day TFC membrane, the 300 litres is rated at 50 psi (350 kpa) but will produce up to 450 litres per day higher pressures, what this means is the system will fill faster than most systems on the market. This system has an auto shut-off device that closes off the in-feed supply when the storage tank has filled.

Replacement trio of cartridges (ROCDU-02) which is the annual change are $55.00

Optional with in-line re-mineraliser (alkalizer) making it a 5 stage extra $30.00

See faucet (tap) range, click here to view. Faucets

Supplied with QMP-300-HP U.S.A. made housing 10" Australian Standards AS3497 with 1/4" NPT threaded ports. This housing is tough with a burst strength of 575psi (4000kpa) and is tested to AS3497 which means it has been tested from 0 to 700kpa and back to 0 kpa 100,000 times without failure, cracking or distortion.

With these premium systems we supply the 550kpa pressure limiting valve with dual check valves which is a plumbing code requirement, the valve is also Watermark AS1357-2 licence no 23133as the watermark is also a plumbing code requirement.

We supply the 550kpa PLV with the premium system so the filter system runs faster than other units on the market.

The PSI-021-4P-GM has twin pressure gauges to monitor the pressure difference between the mains in-put pressure and the pressure being applied to the membrane after the two pre-filters, this allows you to monitor what is happening within the system from the outside.

Click here to down load a sample of the installation instructions pdf format

This system also comes with a TDS meter (total dissolved solids) which measures impurities in water in parts per million (ppm), this allows you to easily measure the success of the membrane and re-assure you all is working correctly.

All components are NSF certified to standards 042, 053 & 058. Highest Quality QMP-300 US housings, standard size 10 inch (9 ¾" (248mm) NSF certified (worlds leading certification authority) NSF/ANSI standard 042 certification, also tested and certified to Australian Standards 3497,

Removes 92 to 95% of Fluoride.

For membrane treatment rates click here.

Click here to jump to the re-order for the correct annual trio pack of cartridges.

Click here to jump to the re-order for the correct membrane changed usually at the 4th year.

If your system has the in-line re-mineraliser/alkaliser fitted click here for that replacement cartridge, normally changed every second year.

1 Micron food grade polyspun sediment filter 9 ¾" (248mm) (standard size) U.S. made

Omnipure OMB934-5M coconut quality carbon cartridge 9 ¾" (248mm) 37,000 litres chlorine rating, U.S. made

Genuine Omnipure CL10RO- Coconut carbon post filter, highest quality possible. U.S. made

Genuine Dow Filmtec TFC Membrane (standard by which all other membranes are measured)

Main filter unit size, 42 cm high, 35 cm wide & 14 cm deep. 9 litre stainless steel storage tank (exceeds drinking water guidelines) NSF Certified. If space is an issue we also offer a 4.2 litre or 12 litre tank

Click here for tank details.

Premium systems now have the lowest waste ratio of all systems on the Australian market, using a Patented combination membrane flushing valve/flow restrictor means the waste ratio is about 50% less waste than other brands, waste ratio is now about 1 to 1.

Click here to obtain more information about waste ratios

Installation choice 1/2" tee olive fitting, 3/4"dishwasher adapter or 1/2" easy fit braided line flick mixer adapter, our systems take the average handyman 1/2 to 1 hour to install.

Mains connect systems click here to view how each are installed

550 kpa pressure limiting valve, genuine QMP Stainless Steel dedicated faucet. Housing spanner to ease cartridge changes. 

10 year warranty

Click here for selection Advice

PSI Systems are Better Than Other Brands, click here to find out why

All reverse osmosis systems require a minimum pressure of 40 psi (280kpa) with 50 psi (350kpa) or more is ideal. If you are unsure what your pressure is check with your local Council or water authority.

Product comes complete, ready for installation.

Substance treatment rates below for TFC reverse osmosis, click here for a full list in PDF


The PSI-021-4GM is a 4 stage undersink premium reverse osmosis system with monitoring for pressure and purity.


The first gauge measures the mains pressure which can vary at different times of the day (and that is why there are two gauges) and the second gauge measures the pressure being applied to the membrane after the two pre-filters, the difference between the two gauge readings will indicate the amount of pressure drop being applied to the membrane as a result of dirt that is deposited on the pre-filters resulting in partial blockage. This is handy as a diagnostic tool if the system was not producing the normal flow rate.


The TDS meter (total dissolved solids) is a handy device to check the purity of the water to re-assure you that all is working correctly. The hardness (which is what a TDS meter measures) of mains water will vary with the time of your and is usually highest in the summer months so it is advisable to check both the in-feed TDS and the out-feed TDS when checking the production water.


This premium system also has an on-board membrane flushing valve making it very easy to self maintain. This flushing process maintains high purity by flushing the membrane of any possible deposits such as calcium or salt.


This system is one of the group of premium reverse osmosis systems that we make using the very best of parts from around the world. Quality that is not always obvious by a non expert but things like the pressure gauges are stainless steel oil filled gauges which are the best you can buy which are pressure compensating, in-feed ball valve that is water marked which is an Australians standard requirement but we would estimate only at best 2% of suppliers in Australia would comply with. The tubing used is made by the John Guest Company in Britain and the best in the world being NSF standard 61 compliant and pressure rated at 230psi (1600kpa) pressure, the auto shut off valve is USA made by Hydromatic as is the stainless steel check valve which are the highest quality. The housings are made in the USA by QMP and burst pressure rated at 575psi (4000kpa) which makes them just about bullet proof, the filters are USA made and tested to Australian Standards AS3497, the membrane is USA made by Dow Filmtec and are the genuine article having both a serial number and the hologram on them so you can check they are genuine item yourself on the Dow Filmtec web site and these things have been placed on the genuine membranes as a result of Chinese copies being available around the world.  The quality continues with the faucet (dedicated tap) being Italian, USA or Taiwan made but more important are NSF certified not to contain construction material such as lead. We would estimate that about 90% of the faucets used by water filter suppliers are the non NSF certified ones as they are about ½ the cost wholesale and contain between 6 to 11% lead and appearance is nothing to go by as both NSF and non NSF faucets can look identical as the manufacturers all copy each other in design. The quality of the components goes on with only genuine John Guest and Jaco fittings used and not the standard Jaco fittings but the gripper series, the list of quality parts goes on and on resulting in a strong reliable system.


Product Details

Data sheet

10 Years Warranty
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