RO Perm - Troubleshoot Guide: No Shut-Off

When the wastewater from your RO runs non-stop all day, and cannot shut off even when the tank is full.

3 possible causes:

  • Broken or insensitive Permeate Pump (cannot shut off).
  • Broken or clogged Check Valve.
  • If your RO feeds multiple output points, maybe one of these output is leaking.

You can do the test below to find out which part is broken or insensitive.

Test Check Valve and Permeate Pump:

  • Let RO fill up your tank.
  • Turn OFF the feed water supply to the RO.
  • Open the tank valve.
  • Remove the RO�s Black drain line from the drain saddle (on your drainpipe).
  • Check this Black line to see if there is any water-draining out.
  • If there is water draining out from the line --> This means the Check Valve is bad. It has failed to shut off. It is allowing the water in the tank to back flow out into the black drain line.

Solution: Replace Check Valve (see diagram point E)

  • If there is NO water draining out from the black line. This means the Permeate Pump is bad, the shut-off valve inside the pump has failed, so waste water cannot shut off after the tank is filled. The Check Valve is OK, it is not the cause.

Solution: Replace the Permeate Pump (see diagram)

Order Check Valve online at this link: Item#  Check Valve  $9

Order Permeate Pump online at this link:

Check 2nd output line for leaks:

If your RO feeds a 2nd or 3rd output point, check those lines and fittings for any possible pressure leakage. Any slight leakage in the line will cause the RO to not shut off.

Please Note:

RO shut-off failed:  Depletes stages 1, 2, 3 Prefilters 

Since your RO could not shut off, input water has been going thru the stages 1,2,3 prefilters constantly. If this has gone on for more than 1-2 months, chances are these prefilters are depleted from the continuous draining of water in the last few months. So we think you should change the 3 prefilters now if possible, so they can protect the membrane.

Reminder: Check Membrane with TDS meter

If you have a TDS water tester, you can check the stage-4 Membrane to verify membrane is still good.

Reminder: Yearly Pre-filter Change Important!

It's important to change the 3 prefilters at least every 12 months. They protect the stage 4 Membrane, which is the heart of the RO system. 

If you forget to change the prefilters timely, they'll get over-depleted or over loaded, this will damage the Auto-Shut-Off valve and the Stage-4 Membrane. So it's very important to replace the 3 prefilters once a year.

End of Test

RO System - Membrane & Filter Change Schedule: There are 5 filter cartridges on your under-sink RO system:

Stages-1, 2, & 3 Pre-filters 
Change every 12 months.
Cost:  $39 per set (1 sediment, 2 carbons) same for all models
Order Item# "FILTER-SET"
Stage 4 RO membrane:
Change every 3-5 years depending on input water quality.
Cost:   $65  (for RO45, RO-PUMP models)
Cost:   $85  (for RO90, RO-PERM models)
Order Item# "MEM-45"  OR  "MEM-90"
Stage 5 polish filter:  
Changed once every 3-5 years. 
Cost:  $10  (same for all models)
Order Item# "5-TCR"

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