Reverse Osmosis Waste

Reverse Osmosis systems by the way they work do waste a certain amount of water, and PSI Filters reverse osmosis systems are very efficient by comparison to many others on the market.

The normal waste ratio to product water for a residential type of reverse osmosis system is 3 to 1 and even as high as 4 to 1. (that's 4 litres of waste to 1 litre of product water)

These ratios originate mostly from Northern America where the water is on average much harder water than here in Australia, so most systems are configured as 3 to 1 here.

PSI Filters & Boss Water Systems Australia have been testing various waste ratios in areas around Australia for the past 2 years and as a result of testing and using patented flow restrictors are able to offer far lower waste ratios than our competitors units, generally 50% to 80% less waste and still maintain purity. This lower waste results in less total water passing through the pre filters which reduces operating costs but with less waste water there is also the environmental aspect as well as lower water usage.

Our waste ratios are calculated at 50psi water pressure & 25 degrees, at higher pressures the waste ratio is even lower as the membrane produces at a much higher rate at higher pressures, almost double at 90psi but the waste ratio doesn't increase at the same rate as pressures increase. There are some others that claim low waste but they are rating the waste ratio at the pressure limiting valves pressure rating not at 50psi. There will be an increase in the waste ratio just as the tank nears it's full capacity due to back pressure.

Waste water is a necessary evil as a reverse osmosis is a true water purifier, it selects the purest water molecules and rejects the contaminated ones. A carbon water filter is very successful at removing things like chlorine, pesticides, herbicides and in some cases lead and heavy metals but it is a type of strainer and the contaminates are held within the carbon and if you try and make the filters last longer than what would be considered normal they can release some of the toxins that they have adsorbed.

Reverse Osmosis systems are different to the standard type of carbon water filters as the contaminated water molecules are not held within the reverse osmosis membrane but are contained in the waste water and are flushed away out of the system.

Low waste units are suitable for Mains water supplies in metropolitan & country areas meeting the drinking water guidelines, bore and dam water supplies require a higher waste ratio and pre UV sterilisation.

Reverse Osmosis waste water is only waste if it is sent down the drain, we have many fittings and tubing options available to re-use the waste water in the garden. Ring and discuss what you need and we will help.


  • Dear Stephanie, Just a brief note to thank you for your excellent service and for the twin under sink system that we purchased. We were delighted with the quality of the system including the ceramic disk Touch-flow brand faucet. The unit arrived...

    Ray Fallu, Victoria
  • Hi Peter Just to let you know that the part arrived safely. Our local post office was closed until last Tuesday so picked it up then and installed it over the weekend. The system works very well and the water is coming through clear and tasting...

    S Richards, Mylor, SA
  • Thought I would give you some customer feed back which I seldom do but I am impressed with both the product and service. I purchased a whole house system about a month ago and had it installed by a local plumber who was also impressed with the...

    Fred B, .
  • This is the first time I have offered endorsement of a commercial enterprise. In this instance an endorsement is well placed. My customer connection with PSI Filters began about 8 years ago. At that time PSI Filters were one of relatively few...

    N McLeod, Townsville, Nth Qld