Why Is My Reverse Osmosis Constantly Draining And How To Shut It Off?

Reverse osmosis is a  water purification system ; it uses a semi-permeable membrane to filter out the particles and molecules from the water that are unwanted. These unwanted particles may include sediments, contaminants, dirt, chlorine, or salt in the water.

As we all know it is a purification system and there are possibilities to occur some problems that cause improper functionalities of the system. At this point, we need to fix our osmosis system.

To effectively fix your reverse osmosis system, you must first determine the cause of the problem. Since the numerous components of an RO system work together to produce clean water, a single problem can be caused by a combination of them.

To eliminate potential errors, reverse osmosis troubleshooting requires a systematic approach. In this context, I am going to tell you the best possible solutions if your osmosis system constantly draining.

This article may also helpful for you: How To Replace Reverse Osmosir Filters

Basic Components of a Reverse Osmosis System


Pre-filters protect against sediment and chlorine. The flow limiter can be damaged or obstructed by sediment. By oxidizing the membrane material, chlorine can ruin it. On the way to your faucet, ice maker, or refrigerator, post-filters ensure a cool passage through the carbon.

Check Valve:

The permeate outlet of the diaphragm (filtered water) is equipped with a non-return valve. The non-return valve protects the diaphragm from backpressure and at the same time increases the pressure in the tank, opening the ASO valve. The RO system will not stop without it, which can lead to membrane failure due to reflux.

Automatic Shut-off Valve:

Supply and tank pressures are monitored by this device. The ASO valve closes hydraulically when the tank pressure reaches 2/3 of the pipe pressure, stopping the flow of water.


The RO diaphragm is driven by the pressure that drives water through the system. Water production and TDS discharge are minimal without sufficient drive pressure. The production rate is influenced by the inlet pressure and the water temperature.

Flow Restrictor:

The flow limiter creates resistance on the RO membrane and effectively measures the flow of water to the drain. Its scale is according to the initial index of the membrane, and if it is not correct, it can interfere with the exit of the membrane.

Storage Tank:

A pressure tank (hydropneumatic) is a type of storage tank used with RO systems. There are two chambers in the tanks: one for water and one for air. The separation membrane extends into the airside when the tank fills with water, increasing the pressure on that side.

The water is pushed by this pressure from the tank back into the faucet or another point of use. Little or no flow at the faucet can be caused by a loss of air pressure before the charge or the integrity of the membrane.

Drain Saddle:

RO systems have a drain that transports pollutants away. A drain saddle connects the water pipe from the air gap tap to the sink drain pipe.

Feed Pressure:

The feed pressure of the water that enters the RO system is essential to its operation. It is crucial to think about how high TDS and low pressure can affect the operation of a system.

Air Gap:

Backflow prevention is necessary on any cross-connection (supply on one side, drain connection on the other) to prevent drainage or sewage from flowing into the drinking water supply, following plumbing rules.

Why Is My Reverse Osmosis Constantly Draining?

The pressure in a reverse osmosis system is what makes it work. Simply put, the feed water goes into the unit, where it is cleaned and then kept for later use in the storage tank.

When the storage tank reaches capacity, an automated shut-off valve (ASO) closes. The valve prevents any additional water from entering the system. The check valve is a second valve that prevents discharge water from flowing along the drain line.

There could be a problem with the ASO valve or check valve if the discharged water continues to flow into the drainage system. As a result, there may be a waste of water.

What are the Causes of Reverse Osmosis Constantly Draining

Let’s discuss some main causes of the RO system constantly draining:

Check Valve:


If the check valve fails, the RO system cannot reach the stop pressure. As a result, more water flows into the drain pipe. This problem can be solved by replacing the check valve with a new one

ASO Valve:

Even when the storage tank is full, a damaged ASO valve allows additional water to enter the reverse osmosis system. To reduce the pressure, unplug the valve and replace it with a new one to resolve the issue.

Flow Restrictor:

When your system’s flow limiter is worn out, a large amount of drained water flows through the drainage pipes and causes a lot of noise. Replace the worn-out restricted with a new one to fix the problem.


The tank does not fill up fast enough to maintain the required pressure. If there is a problem with membrane manufacturing, a flow test should reveal it.

How To Troubleshoot the draining problem of RO System?

Here I have possible solutions that will help to troubleshoot the problem of the RO system not shutting:

  • Measure the pressure in the storage tank, when empty, with a pressure gauge. The pressure in the tank should be about 6-8 psi. They must be ready for printing if the pressure is too low.
  • Did the problem recur a few days later? This indicates that the bubble in the tank has burst and can no longer hold air. You have no choice but to replace the entire tank.
  • Is the tank pressure within the acceptable range? The shut-off valve or check valve is most likely defective and you need to replace it. 
  • The RO membrane deteriorates. You should replace it.
  • The problem causes by a worn flow limiter in the drain pipe. Remove and replace the restricted.

Check out the review of APEC Ultimate RO-90 


If you are living in an area where you need a water purification system, then I must say Reverse Osmosis System is the best one. If you already have this one, then its maintenance is necessary. As it is an electric system it means, it can also catch by different problems but at this time never panic at all.

Patiently check the entire system and monitor its all activities. Try out given possibilities to troubleshoot the draining system.

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