Change the PP filter housing to a transparent one so I can see how dirty the filter is.
2. Change the 5 micron PP filter to a ceramic filter that filter to 0.1 micron. This should make the membrane last a bit longer. The ceramic filter can also be cleaned and used again and again The drawback is that it is clogging up a lot faster than the PP filter so it need to be taken out and clean every 2-3 months. 3. Now I got a spare housing so I put a DI resin filter in it. Use it as one of the post filter. Now I got a spare housing so I put a DI resin filter in it. Use it as one of the post filter. This should improve the TDS a little bit.
4. Put hollow fiber ultra filter in front of the low pressure switch. UF filters the water down to 0.01 micron. Again this should prolong the membrane life.
5. About three months after I have done the above modification, I managed to get a permeate pump from Ebay so I put that in as well. This should and does reduced the waste brine water from the RO membrane.
The housing got one inlet and two outlets because it is basically the RO membrane housing. To use this housing with the UF, one of the outlets has to be plugged off. However I put a pressure gage in instead. This should help monitoring the filter and see if it get clogged up and need replacement
Below is the picture of the system after the modification. To my surprise the TDS is still around 10-12 ppm. This perhaps because the new membrane I put in was 50GPD instead of 75GPD that came with the original unit. I am not going to change the membrane again anytime soon so I guess we will stuck with this one for a year or two.
Schematic of the modified system is below:
The permeate pump I got is a second hand one from Israel. The manufacturing date was 2012 so it is doubtful that it will last very long. Using bath room scale to weigh to brine discharge before. After installation show that it save about 5 liters of water for every tank of RO water. The discharge was 13 kg before and 8 after the installation. The pump actually work as advertised. I empty the bladder tank for each test and RO membrane housing then fill it back up so the back pressure on the membrane during the test covers the whole range of operation. In real usage where only a small amount of water is drawn out each time and the pressure is hovering on the top of the range, the waste water could be much more then the test and the saving from the permeate pump could be much more accordingly.
This will reduce the water that go through all the pre-filtes so they should last longer as well.
Having said that, the system came with auto flush valve. Every time it starts it will waste some water flushing the membrane. Without the pump, I have to draw out about a liter of water before the high pressure switch kick start the bump. With the pump, even a small amount of water filter element drawn from the system will cause the pump to start so the waste from the flushing could be much more.
All in all, I am happy with the pump but if it breaks down, I wont replace it. On my setup the discharge go back to the underground water holding tank that feed the whole house so it doesn’t matter much with or without the permeate pump. The system is truly zero waste either way.
One of the things people complaint about the pump is the noise. It makes loud clicking noise when it is working. For me it is not a problem. You can listen to the video below. Decide if it is going to be a problem for reverse osmosis membrane system you.
One drawback from all the mods I did is that the booster pump has to work much harder now. It actually make a bit of noise after all the mods. It might not last long be we’ll see.