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RO Pump - 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.

There're 3 valves that control the RO's shut-off function:

See diagram below to identify the valves.

1. Electric Shut Off (ESO) valve: This valve shuts off the pump when the tank is filled.

2. Tank shut off (TSO) valve: This valve shuts off the tank when the tank is filled.

3. Check Valve(Point E): This valve helps tank build up pressure (to 40psi) at which point the TSO will shut to cut off input into the tank. Once the TSO shuts off, the ESO will follow suit and shut down the pump.

If one or more of these valves go bad, cannot close, pressure cannot build up, then the
the pump & waste water will keep running non-stop.

You can run 2 tests:

1) Test RO's Shut off function:

- When RO is making water, the pump is working, and the waste water is draining.

- Close the tank valve to imitate a "tank full" condition.

- If the RO stops making water, the pump & waste water stop running --> this means the RO is shutting off OK. All valves are working fine.

- If the pump & waste water keeps running, cannot stop --> this means RO cannot shut off. We need to test the Check Valve & the TSO/ ESO valves.

2) Test Check, TSO ESO Valves:

- Let RO fill up your tank.

- Turn OFF the cold feed water supply to RO.

- Open the tank valve.

- Remove the ROs Black drain line from your drain pipe.

- Check this Black line to see if there is any water draining out from this line.

- 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 drain line.
Solution: Replace Check Valve

- If there is NO water draining out from the black line --> This means the Check valve is OK. It is either the TSO and/or ESO valve is bad, they fail to shut off when pressure in the tank is built up.
Solution: Replace TSO valve and ESO valve (Contact us)

3) Check your extra output points:

If your RO feeds water to more than 1 point (icemaker, coffee maker etc.), make sure these output lines and T-fittings are all air-tight, no leaks. Any small leak in these lines will cause the pressure in the RO system to not build up, and the RO cannot shut off.

----- End of Test -----

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

If your RO cannot shut off for more than 3-4 weeks, chances are the stages 1, 2, 3 prefilters are depleted from the continuous draining of water. In that case, you should change the 3 prefilters now so they can protect the membrane.

You should also test the membranes condition with a TDS meter (if you have one), to make sure the membrane is still in good condition.

Reminder: Yearly Pre-filter Change Important!

It's important to change the 3 prefilters at least every 12 months. Forgetting to replace them timely will damage the stage-4 membrane and hurt the shut off valves.

Water flows through the RO head as follows:

A: Input water enters stage-1 sediment filter at point A.

ESO: From A, input water enters the Electric Shut Off (ESO) valve.

P1: From ESO, water enters the booster pump at port P1.

P2: With boosted pressure, water leaves the pump at port P2, then enters stage-2 filter.

B: Passing through stages 2 & 3 filters, water leaves stage-3 filter at port B.

D: From B, water enters the Membrane housing at point D (membrane housings cap).

W: Waste water generated by the membrane drains out through point W, and to the drain pipe.

E: Pure water from the membrane exits the housing at point E.

Check Valve: At point E, there is an internal Check Valve encased in the L-shaped plastic fitting. This valve prevents water in the tank from back flowing into the RO system. It also helps the RO shut off when the tank is full.

T1, T2: Pure water from point E enters the TSO Tank Shut Off valve at T1, and exits at T2.

TSO: The TSO Tank Shut Off valve shuts off the tank when pressure inside tank reaches 40psi (pre-set).

F, G: Pure water from T2 passes through points F & G, and enters the pressure tank.

H: When pure water is dispensed, it leaves the tank via the Yellow line, passes through the Stage-5 filter and exits at point H, then flows onto the RO dispensing faucet.