Reverse Osmosis system continually draining


Old 12-28-13, 03:59 PM
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Join Date: Apr 2012
Posts: 11
Reverse Osmosis system continually draining

I have a TGI-WIN 545 5 stage RO system. The system came with the house. I don't have any information on the installation or maintenance of the system. We had been in the house for just over a year and a half when the water started not tasting as good as it used to. Last August (2013), I replaced the filters and RO membrane. I replaced my old RO membrane (MM-TFF 45/75) with a Filmtec 50GPD TFC. I also replaced my existing capillary flow restrictor with an inline 500 ml flow restrictor as recommended for the 50GPD RO membrane.

After replacing the filters and RO membrane, I noticed that the drain water seemed to be running a lot more than before. Eventually I suspected that there was a problem with the ASO valve. I took it apart and found that one of the diaphragm was slightly out of shape. I re-shaped it and put it back together and ran the system. It didn't seem to change much. Still the waste water ran continuously.

From there, I decided I would try replacing the ASO valve. I replaced it with this unit: Auto Shutoff Valves ASO ASV For Reverse Osmosis RO Water Systems. This ASO valve was a bit different than my old one. The IN and OUT ports on the high pressure side were on the same side of the valve where on the old valve, they were on opposite sides. So I had to re-run some of the old tubing in order to get them to loop around to where they needed to go. Anyway, after getting everything all hooked back up, the system is still doing the same thing, just draining water continuously.

For testing, I have turned off the tank valve and the source valve from the tap. Then I turned on the tank valve and no waste water drained out. My understanding is that this indicated that the check valve on the RO housing is good. Then I shut off the tank valve and opened the source valve and waste water started draining immediately. My understanding is that this indicates that the ASO valve is bad. However, the original valve and the replacement are displaying the same results, so I am questioning if this is a correct assumption. Or could there be something else to consider?

I don't have a pressure gauge on the system to see if the problem is in the pressure of the source. I'm wondering if anyone has any ideas on what else I could check first.

Another thing I noticed is that, sometimes, when I would turn on the source valve, the tube coming from the ASO valve to the tank/faucet line, would vibrate, sometimes loudly to where I could easily here it. I believe this indicates that the valve is trying to shut off or almost shutting off but can't quite make the shutoff. This happened with both ASO valves but not all the time.

Any ideas?
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Old 01-11-14, 03:49 PM
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Join Date: Apr 2012
Posts: 11
More information... So I have hooked up some pressure gauges to the system and took some readings. I'm showing that the input pressure is 60-65 psi but the output from the pre-filters is only at 10 psi. Does this indicate that the filters need to be changed? So, on the high pressure side of the ASO, its running at 10 psi into the RO membrane. Then, on the low pressure side of the ASO, its running at 3 psi.

Over the last couple of weeks, the system has been steadily decreasing in product water output. It is now only producing about a cup or two every few hours.

So I guess a couple of clarifying questions...

1. Should the pressure on the high pressure side of the ASO equal that of the supply side? In my case, does the difference indicate that the pre-filters need to be changed?

2. On the low pressure side of the ASO, should I expect to see the pressure steadily increase to match that on the high pressure side? I'm assuming that matching pressure would cause the ASO to shut off. If the pressure is not equal then I'm assuming the ASO will not shut off and thus the cause of my continual waste water.

3. When I replaced the RO membrane, I went from a MM-TFF 45/75 to a 50 GPD TFC (TW30-1812-50D). With the old membrane, I had a capilary flow restrictor. I removed this and replaced it with a 500 ml PFR402Q-500 flow restrictor. I'm showing that the TFC membrane is rated at 50 psi while the TFF membrane is rated at 60 psi. Do I have to go back to the TFC membrane?

4. When I replaced the pre-filters, I wasn't sure what I had before as they weren't labeled that I could see. I ended up getting a Purtex 5-micron sediment, 5 micron carbon block and a 0.5 micron carbon block, installed in that order starting from the water supply. Did I get this order incorrect? Should the pressure from the pre-filter output match that of the source input?
Old 01-31-14, 09:26 PM
Thread Starter
Join Date: Apr 2012
Posts: 11
Looks like it was a bad ASO valve. By the time I replaced the ASO valve, the filters must have been clogged. I ended up removing the filters and the RO membrane and running the system with the pressure gauges. With the new ASO valve, everything worked as expected. Once the pressure on the low pressure side of the ASO got to between 32 and 42 PSI, the ASO shut off.

I ended up replacing all the filters and the RO membrane again.... Now everything is working as expected. The pressure gauges are worth their weight in gold... I ended up getting 4 gauges and placed one at the inlet, one at the outlet of the filters, before going into the high pressure side (HPS) of the ASO, a third gauge on the other side of the HPS of ASO before going into RO membrane and a fourth gauge on the low pressure side of the ASO between the tank and the polishing/finishing filter. It may be overkill but it is nice to be able to quickly identify any problems.

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