Domestic Reverse Osmosis Troubleshooting Guide

Domestic Reverse Osmosis Troubleshooting Guide

The following information and chart listed below is intended to serve only as a general guide for determining common problems and solutions.

Although the information provide below will help to to identify your problem about your system, you may experience a problem that is not listed below. If that might be the case, feel free to contact us for further assistance.

Possible Cause

Feed water valve is plugged or close.


Open valve or unclog.

Sediment/Carbon Pre-filter or Carbon Post Filter is clogged.

Replace filters.

Low incoming water pressure.

Incoming water pressure must be above 40 PSI. Install a Booster Pump or Permeate Pump.

Reverse Osmosis Membrane is fouled.

Make sure incoming water pressure is within operating limits. Make sure drain line is not clogged. (See High TDS) Correct cause of fouling and replace RO Membrane.

Air pressure in holding tank is incorrect.

Empty water from holding tank. Air pressure in valve stem should be between 7 – 8 PSI

Air bladder in holding tank is ruptured.

Replace holding tank.

Holding Tank valve is closed.

Open valve.

No water to drain. Drain Flow Restrictor is clogged.

Replace Drain Flow Restrictor.

No water to drain. Air Gap Faucet is clogged.

Clear or replace Air Gap Faucet.

Check Valve on RO Membrane Housing is stuck.

Replace Check Valve.

The Automatic Shut-Off Valve is Malfunctioning.

Replace Automatic Shut-Off Valve.

Storage tank is depleted.

Increase product water storage capacity and/or install membrane and flow control with higher output rating.

Possible Cause

Bad membrane.


Use Tds Meter to check membrane. Replace membrane and sanitize when below 75% rejection.

Water supply.

High oxygen content. Tiny frozen bubbles.

System is still new.

Some refrigerators freeze differently, leaving the ice cube looking cloudy. Let cube dissolve in glass of water. If just air, will float to surface and dissipate.

This is normal and should clear up in two weeks.

Possible Cause

Air gap faucet.


A little noise is common with air gap faucets. Check manual to be sure installed in proper location. Allow two weeks for air to work out of system.

Drain tube.

Check that drain tube from faucet is continuously down hill to drain saddle. Loops or dips will cause noise and back up in drain line to faucet.

Possible Cause

O ring not sealed properly.


If O-ring is damaged, replace.  If dirty, clean, lubricate with silicone lube and retighten filter housing sump.   Hand tighten firmly.  Do not use a filter housing wrench to tighten.

Possible Cause

Clamp slipped on drain saddle preventing proper flow to the drain.


Align hole in drain saddle with hole in drain pipe.

Drain tube loops or dips creating a backup.

Shorten drain tube from faucet until smooth downhill flow to drain saddle.

Restriction in drain tube. Remove gunk or food particles in tube or replace the tube.  Just because you are getting water out of the drain tube does not mean that it is coming out fast enough.  Any backup in the tube will cause the faucet to leak.

Disconnect drain tube and clean out restriction. (Food particles from garbage disposal).

Restriction in drain hole inside the hole on the back of the faucet.

The drain hole in the base and on the rear of the faucet must both be clear and unrestricted. Clean as necessary.

There is foreign matter in Holding Tank.

Clean, flush and sanitize the Holding Tank. Replace filters.

Product water and Drain water lines are reversed.

Correct plumbing.

Dissolved gases in feed water.

Pretreat feed water to remove gasses.

Increase in Product Water TDS.

See High TDS in Product Water Section.

Possible Cause

Bad membrane.


Test membrane with a TDS tester meter.  Replace RO membrane when below 75% rejection and sanitize.

Filters have expired.

Replace water filters. Should be replaced every 6 to 12 months.

Little water use.

Drain entire tank. Should be done once every week to keep stored water fresh.

System needs sanitizing.

Sanitize (see Sanitizing Instructions) and replace filters.

Possible Cause

Air pressure in holding tank is incorrect –Over / Under pressurized tank.


Open faucet and empty water from holding tank. Shut off feed water to system and remove holding tank from under sink. (The tank is easier to work on.)

Locate the air valve stem (just like on a car or bicycle tire) and add air. If there is still water in the tank, continue to add air until all the water is removed.

Once all the water is removed, continue to add air and pressurize to 8 PSI.

Re-install the tank under the sink, turn on the feed supply to the system and allow the tank to fill.

Incoming water pressure is below 40 PSI.

Increase pressure to 40 PSI.  May require a pump.

Tank valve not open.

Open tank valve.

System takes 3 to 4 hours to completely fill.

Bad water storage tank.

Replace storage tank, If not bad, check that tank air pressure is between 7 PSI when empty.

Filters clogged.

Replace water filters.

Kinked tube.

Un-kink tube. If damaged, replace tube.

“Fouled” membrane.

Replace RO membrane.

Heavy water use. Holding Tank is empty.

Allow Holding Tank to refill.

The Faucet is out of adjustment or faulty

Repair or replace Faucet.

Possible Cause

Prefilters are partially plugged. Lowered water pressure prevents the hydraulic shut off valve from actuating.


Replace prefilters.  To check if if it is the pre-filters you can remove them and operate the system without them until it shuts off.  This will confirm that the filters are the problem.

Auto-shut off valve not working.

Replace auto shut off valve.

Low incoming water pressure.

Increase incoming water pressure to 40 PSI or better.  This may take a pump.

Low tank air pressure.

Check tank pressure with air pressure gauge.  Fill to 7 PSI.

Tank bladder is ruptured.  Is the tank heavy after draining out all water?

Replace the tank.

Flow restrictor worn out.

Replace the flow restrictor.

Membrane is bad (fouled).

Use TDS tester meter to check membrane.  Replace membrane.

Possible Cause

Normal RO process.


Your RO system makes water a drop at a time. 4 gallon storage tank should be full within 6  hours.

Low water pressure.

Increase incoming water pressure. This may require a pump.  Check for kinked tubes.

Filters plugged.

Replace water filters.

Fouled  membrane.

Replace RO membrane.

Low Tank air pressure.

Check tank pressure with air pressure gauge.  Fill to 7 PSI.

Possible Cause

ASV (auto shut-off valve) is defective – High pressure inlet water bypassing the rubber diaphragms in the ASV and entering the Permeate (RO) water line.


Replace ASV auto shut off valve.

Water may be bypassing the Brine Seal –(large rubber ring around the outside of the membrane).

Remove and reinstall membrane making sure that the Brine Seal is making contact with the inside of the membrane housing wall.  Seal the Brine Seal with Silicone sealant.  Clean the inside of the membrane housing wall when the membrane is removed.  Examine membrane housing to see if it has warped.  A membrane’s brine seal will slowly form to the contour of a housing that is warping.  So the old membrane might fit while a new membrane will have trouble fitting in a warped housing.  Replace a warped membrane housing.

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