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I was having issues with my RO filter a couple of months ago, changed all the filters, and that seemed to fix it. But then a couple days ago, we seem to have lost pressure in the kitchen spigot from the RO filter. Any ideas what might cause that to happen all at once? There is still occasionally some water that comes out - say, in the morning we can fill a water bottle or two slowly. But then during the day, it comes out at a trickle if at all.

Update based on questions from @MTA :

The RO pressure tank is not full of water (so I don't think the bladder has ruptured).

I don't have a low-sensitivity air-pressure gauge, but my regular one seems to indicate it is somewhere between 5 psi and 10 psi, so it does not seem that the tank has lost all pressuer.

I just turned on the spigot and was getting a slow stream of water. I then went to the basement and checked, and the pressure pump did not seem to be doing anything (it was still and room-temp to the touch). After a few minutes, the slow stream slowed to a dribble and then to a few drops per second, and the pressure pump still does not seem to be doing anything.

We left the spigot open over night, and it managed to fill up (and overflow) a 2 liter jug.

Further Update:

After following MTA's diagnostic advice, I ended up cleaning out the RO membrane housing (which seemed to have some mineral buildup in it) and replacing the RO membrane. This seems to have solved the problem.

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See the diagram from your manual below.

Your permeate pump may have stopped running (it could be stalled or burned out), its diaphragm could have failed so it can't produce pressure, or its internal pressure switch may have failed. See if it is warm, vibrating or just dead when all water has been delivered from the spigot.

Your storage tank bladder could have failed, leaving no empty space to store water. If you were recently getting bubbles from the spigot, this is a sign of bladder failure. See if the tank is extremely heavy as if it is full of water after all water has been delivered from the spigot. Alternate cause: all air pressure has leaked from the Schrader valve on the storage tank. Air is usually maintained at 7-10 PSI with the tank empty.

The unnamed part with two blue and two red lines in the diagram, variously called a "automatic shutoff valve for RO" (or similar) could have failed. This part allows water to flow to the RO membrane and make filtered water when the pressure in the tank is less than half of your source water pressure.

Your drain restrictor could be clogged or stuck, preventing brine from leaving the apparatus and stopping water production.

Your check valve could be stuck closed, with the same effect.

It may be diagnostic to run out all the water from the spigot and see if water continues to flow from it very slowly, either in a slow stream or just a fast drip. That would indicate that the RO membrane is getting water but one of the above parts is not permitting full production and storage.

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  • The RO pressure tank is not full of water. I don't have a low-sensitivity air-pressure gauge, but my regular one seems to indicate it is somewhere between 5 psi and 10 psi. I just turned on the spigot and was getting a slow stream of water. I went to the basement and checked, and the pressure pump did not seem to be doing anything. After a few minutes, the slow stream slowed to a dribble and then to a few drops per second, and the pressure pump still does not seem to be doing anything. We left the spigot open over night, and it managed to fill up (and overflow) a 2 liter jug.
    – Doug
    Commented Jun 23 at 15:25
  • @Doug Suggest you turn off water and disconnect red line to RO Module, hold it in a container and turn on water. You should get high pressure and flow, say close to a gallon per minute. If flow minimal, turn water off, disconnect red at Auto Shutoff Valve IN, water on and check flow. If still minimal, sediment filter is clogged but if now good, Auto Shutoff is faulty. If first test of red at RO was good flow, I think your permeate pump is faulty. With no pressure in the tank, it should be running. I don't know this particular pump model but it seems clear. Anyone else?
    – MTA
    Commented Jun 23 at 16:39
  • @Doug At some point you'll need to get a digital tire gauge, empty the tank of all water and set tank air pressure to 7-10 PSI or whatever your manual recommends. Use a bicycle pump or portable air tank. This won't fix your current problem.
    – MTA
    Commented Jun 23 at 16:42
  • I got a low-pressure gauge and it showed that I had about 6 PSI in the tank. I pumped it up to 8.
    – Doug
    Commented Jun 25 at 0:23

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