sudo apt-get update # Fetches the list of available updates
sudo apt-get upgrade # Strictly upgrades the current packages
sudo apt-get dist-upgrade # Installs updates (new ones)
After about a year the TDS from the RO filter creep up to around 25 ppm so I thought it was a good time to get all the filters changed including the membrane. I decided do a little modification to the original system in hope of improving it and, of course, having fun. Ignoring my wife advice to leave it alone, these are what I have done to the system:
Change the PP filter housing to a transparent one so I can see how dirty the filter is.
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.
Now I got a spare housing so I put a DI resin filter in it and use it as one of the post filter. This should improve the TDS a little bit.
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.
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 UF filter I put in is pictured below:
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 and 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 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 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 and decide if it is going to be a problem for 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.
I bought an under the sink RO water filter system over a year ago. The system cost about 2700 THB in Thailand which is around 75 USD. The price is pretty good when you know where to go. The price in the shopping malls and big water company could be anywhere around 5000 to 10000 (140 - 280 USD).
There were a few model to choose from. Without much knowledge of how the system works, I just went to the cheapest one and avoid the fancy electronic system with lot of flashing LED.
After about a day of drilling, piping and power cable connection I got it up and running. The TDS was about 10-12 on the first installation. My wife said the water taste much better than the water from our previous 3 stainless steel cylinder ceramic filter system.The system filter to 0.1 micron compare to 0.0001 micron of the RO system.
The RO system come with high/low pressure switch, booster pump and also auto flush valve. I thought the system was 50 GPD but only after I replaced the membrane with 50 GPD that I realized it is actually 75 GPD system.
Pictures of the installation and the schematic are below.
The system came equipped with auto flush flow restrictor, high and low pressure switch.
The high pressure switch cut the pump off when the tank is full and start the pump when the tank need top ups. The low pressure switch cut the pump off when there is not enough pressure on the inlet so the pump would not be starving. Auto flush valve with flush the membrane for a few seconds when the system start and then restrict the flow to build up pressure. This is pretty neat. Most of the systems out there got only flow restrictor and some with manual flush valve.
After 4 months I decided to take the PP filter out and this is what I found:
It doesn't look too bad, especially on the inside:
