The problem with float valves (without the use of a pressurised storage tank) is if you were filling a 100 litre drum about 125 litres of waste water is created with one of our systems but in the U.S. that figure will be about 400 litres. This is because our water is softer and we lower the waste ratio. With an RO with auto shut off without a reverse osmosis pressure tank what happens is the drum will fill to say the last 20mm fine but as the float valve starts to choke off the product water the waste is at 100%. At the last 1mm the float valve is allowing drips but because the drips won’t allow the absolute back pressure to the auto shutoff it stays open with say 300ml of waste and 30ml of product and this gets worse when just drips are supplied to the drum. The waste created to fill the last 20mm would be something like 2 to 3 times the amount to fill up to the last 20mm. When a storage tank is added the excess water being made backs up into the storage tank and when the back pressure from the storage tank equals 66% of the in-feed pressure the auto shut off valve closes and the dribbles and drips to the float valve are supplied by the storage tank.

If one of the final Di cartridge housings contained plastic pillows filled with air rather than resin cartridge that would work because the water pressure would compress the air in the pillows which will create the expansion required to shut the auto shut off valve. This is not as good as a reverse osmosis storage tank but would work.


  • Just want to say thank you for such a prompt delivery of my under sink reverse osmosis system, had it installed in no time and after a few attempts at getting the tubing to stay in place it is working an absolute treat. I had an older system for...

    Colin Sherrott, Lara, Vic
  • Hi Callum   Filter system received. Installed. Working great. Wife very happy as she claims that it is the best tasting water that she has ever had. ( got to keep them happy?). Thanks again, for the prompt and great service. Please list me...

    Peter G, .
  • Hi Stephanie & Peter, Just thought that we'd let you know that we're thrilled to bits with the Twin Under-sink PSI-304 system that you supplied. It arrived yesterday morning, it went in today & the installatiion was an absolute breeze. The fact...

    Tania & John Spencer, .
  • Can I just say we were very happy with our last unit at our previous home, so that\'s why we wont hesitate to get another from your company.

    Bevan, .