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7 Reasons Why Reverse Osmosis System is Constantly Draining

Scott Winfield
Last Updated on
by Scott Winfield

You might not realize it, but the Reverse Osmosis (RO) system at your house is a pretty complex mechanism. Numerous components work simultaneously to give you clean filtered water.

And when a particular component fails to work properly, you might get stuck with annoying troubles like a constantly draining RO system. The specific reason why this happens is not only one but many.

In a nutshell, here are common reasons for reverse osmosis drainage:

  • Low pressure inside storage tank
  • Ruptured air bladder
  • Damaged Shut-off Valve
  • Broken check valve
  • Worn-Out flow restrictor
  • Faulty RO System installation
  • Clogged RO Membrane
Reverse Osmosis
Reverse Osmosis System

First things first, you need to know how the reverse osmosis system works before going into the details. If you learn how the components work, you’ll be able to detect which part of the unit should be fixed or replaced to solve the drainage problem.

As mentioned, a number of units work together in a RO unit. But you only need to know about the storage tank, automatic shut-off (ASO) valve, check valve, and flow restrictor.

So, we will discuss the functions of each component to tell how it might cause RO system drainage and find out the solutions.

1. Low Pressure Inside the Storage Tank Can Cause Drainage

Low Pressure Inside the Storage Tank
Low Pressure Inside the Storage Tank

A storage tank is where the feed water is stored after passing the RO membrane. The RO system uses a high-pressure water pump to flow the water through the reverse osmosis membrane and filters to turn them into pure water.

When the tank is empty, the air pressure inside should be between 6 psi and 8 psi. Maintaining the pressure inside the tank is essential to keep the system running, and low water pressure is the number one cause your RO system might be draining.

You can use a PSI or pressure gauge to test if the pressure is too low. If it’s lower than 6 psi, here’s what you can do to increase it.

The Solution to Low Storage Tank Pressure:

First, you should try to repressurize the RO tank. It’s an easy process and doesn’t require any extra tools. Here’s how you can repressurize the tank pressure:

  • Step 1: Turn off your water supply and shut off the pressure tank valve. Disconnect the tank and take it to a place where you can drain the remaining water from the tank.
  • Step 2: In the beginning, the water drain quickly. But once the water flow decreases, you need to use a bicycle pump to insert air into the tank. The more you pump, the more water will come out. Keep pumping until the tank is empty.
  • Step 3: Now, take the pressure gauge and check the pressure. If it’s too low, you have to repressurize the air pressure valve. Locate the valve stem first and carefully remove its cover. Remember, there’s a second valve that directly reaches the RO membrane. Do not touch the second valve.
  • Step 4: Use the bicycle pump or get an air compressor for pumping air into the tank. Keep checking the PSI gauge to make sure you’re not over-pressurizing it. Otherwise, the tank might rupture.
  • Step 5: When the pressure reaches the standard level (6-8 psi), stop pumping and close the pressure valve. Replace the removed parts and attach the tank to the RO system again. Turn on the flow and check if the drainage system is fixed.

2. Ruptured Air Bladder Can Cause RO System Drainage

Ruptured Air Bladder
Ruptured Air Bladder

Even if the #1 method above works, it’s possible that the water will continue draining after a few days. In that case, maybe the air bladder is damaged, and it can’t hold enough air. RO systems require regular maintenance to keep their components working.

If you don’t maintain your RO unit, the air bladder might rupture due to some physical force or excessive water pressure.

When the air bladder is damaged, there will be little or no flow of water, even if the tank is full. You can easily detect a ruptured air bladder by adding one cup of water to the tank at normal pressure. If the water flow decreases, your air bladder is definitely damaged.

The Solution to Ruptured Air Bladder:

It’s not possible to fix a ruptured air bladder. In this case, the entire RO tank needs to be replaced to solve the drainage issue.

3. Damaged Shut off Valve Can Cause System Drainage

Damaged Shut off Valve
Damaged Shut off Valve

After the filtration process, reverse osmosis water is stored in the RO tank. Once the tank becomes full, the automatic shut-off valve is triggered to close. This way, the valve prevents more water from entering the storage tank.

When the ASO valve gets broken or damaged, additional water enters the reverse osmosis system, and the extra water starts to drain. Detecting a broken ASO valve is easy. First, fill the tank and keep the tank valve open.

Then try to listen closely to see if the water is draining. You can also pull the drain line from the drain saddle to check. If the water keeps draining, this means the ASO valve isn’t doing its work properly, and maybe it’s broken or damaged.

The Solution to Damaged Shut Off Valve:

To solve this problem, you have to replace the broken ASO valve. Follow the step-by-step process given below to get the job done right:

  • Step 1: Dismount the reverse osmosis system to easily access the valve. You can find the valve from the back of your RO unit.
  • Step 2: Got the valve? Now note the correct configuration of the valve so that you can install the new one correctly. The top portion of the valve has in and out markings on it, while the bottom portion has some screws.
  • Step 3: Next, remove all the tubing from the ASO fitting and reconnect them to the new valve. Make sure the connection is done exactly like it was with the old one. When you’re done, mount the RO unit again and check if the water flows directly to the drain or if it’s fixed.

4. Broken Check Valve Might Cause Drainage

Broken Check Valve
Broken Check Valve

As you know, the SO valve shuts automatically and rejects the extra water when the RO tank is filled. The check valve prevents the rejected water from draining.

So, if the valve is broken, the feed water pressure will flow more water into the drain pipe, causing constant drainage.

The Solution to Broken Check Valve:

Check valves are pretty cheap and can be easily replaced. So, it’s best if you can get a new one.

There are two types of check valves available in the market: the straight ones and the 90-degree check valves. We recommend you go for the 90-degree valves as they are easier to install.

5. Worn-Out Flow Restrictor

Worn-Out Flow Restrictor
Worn-Out Flow Restrictor

Another important part of the reverse osmosis system, the flow restrictor, decides how much water will drain at a time.

When the restrictor wears out, the high-pressure water will directly flow to the drain, and the pressure inside the system will decrease too.

The Solution to Worn-out Flow Restrictor:

As a general rule, you should replace the restrictor annually whether it’s worn out or not. To replace your old restrictor, follow these troubleshooting steps-

  • Step 1: First, you have to locate the restrictor. You can find it behind your membrane housing on the black waste water line. Then turn off the feed water and the tank valve.
  • Step 2: As the restrictor is located in the black tubing running between the drain saddle, you need to disconnect the black tubing from the RO system.
  • Step 3: Remove the worn-out restrictor from the black tubing and replace the new one. Make sure the arrow on the restrictor is faced towards the drain saddle. Reconnect the black tubing to the system and check if the water is still draining continuously or not.

6. Faulty RO System Installation Can Cause Drainage

Faulty Installation
Faulty Installation

It’s always better to take professional help while installing the Reverse Osmosis system. Any misplacement of the simplest parts can lead to major issues like constant draining of water.

If you placed the wrong tubing on the wrong fitting or didn’t place a component in the right direction, that’s probably why the feed water is directly going to the drain line.

The Solution to Faulty RO System Installation:

As mentioned, get expert help for installation. If you’re installing the unit all by yourself, make sure you read the instructions carefully and take your time to connect all the components correctly.

In case you have already installed the RO system, dismount it and reinstall it properly, following the given directions in the user manual.

7. Clogged RO Membrane Can Cause Drainage

Clogged RO Membrane
Clogged RO Membrane

Some parts of RO systems need regular replacement to give you clean water. One of them is the reverse osmosis membrane, as it filters dirt, contaminants, and other impurities.

These elements slowly accommodate and blocks the membrane if you don’t flush or replace the membrane regularly. When the membrane gets clogged, the pure water can’t pass and directly goes to the drain pipe. Other than that, the entire system can fail because of the clogged or bad RO membrane.

The Solution to Clogged RO Membrane:

You can easily solve this problem by flushing the RO membrane regularly or replacing it. As the replacement process is pretty complex, we recommend taking help from a professional to do the job.

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Scott Winfield
Scott Winfield
My name is Scott Winfield and researching and writing about water filters and other strategies to purify water has become my full time passion in recent years. I'm glad that you found our site and you can look forward to authoritative and well researched content here to help you get the best in water.
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