My Reverse Osmosis System Keeps Draining

My Reverse Osmosis System Keeps Draining

If you own a Reverse Osmosis (RO) water purification system, then you have some understanding of how the system works and what to expect. However, just like any mechanical or electronic device, you are bound to encounter small issues with your reverse osmosis unit over time. The most common of these issues is that the RO system keeps draining.

Low water pressure, a malfunctioning Auto Shut Off (ASO) valve, a damaged air bladder, a damaged check valve, a worn-out flow restrictor, improper installation, and/or a clogged membrane can all cause your reverse osmosis system to keep draining.

Luckily, most of these issues can be solved on your own. Of course, you will need the right guidance and knowledge, and that is exactly what we can help with! Let’s dive deeper into each of these potential problems and how you can resolve them with ease.

Learn more in my comprehensive article about reverse osmosis.

6 Reasons for My Reverse Osmosis System Constantly Draining

Today, reverse osmosis systems are one of the most popular and sought-after water filtration options for residential, commercial, and industrial applications.

Residential RO filtration systems are made from the following basic components; 3 filters, a check valve, an air bladder, a membrane, an ASO valve, a storage tank, a flow restrictor, and a drain saddle.

In order for a reverse osmosis unit to work efficiently all of these connecting parts need to function seamlessly.

If an RO system keeps draining water, this is a clear indication that one or more of these basic components have failed. The real challenge is finding out which one. In the following sections, we cover how to identify the issue and what you can do to resolve it.

Read my article about troubleshooting reverse osmosis systems.

1. Check storage tank pressure

The most likely reason for your reverse osmosis system to keep draining is due to low water pressure inside your storage tank.

Pressure is what makes an RO system work. If the water pressure is too low, water won’t go through the membrane and would simply flow out from the drainage pipe.

As such, the first thing you should do is check that your high-pressure water pump is functioning properly.

If the pump isn’t a problem, take a pressure gauge and check the PSI levels inside your storage tank.

A 6-8 PSI reading would mean that the tank is empty. Anything less than that would require you to repressurize the RO tank.

If the PSI reading is 35-40 PSI that means your tank is full and your RO unit shouldn’t be producing more filtered water.

However, if your RO unit is still working and draining water, it is very likely that your ASO valve isn’t functioning.

2. Check if the auto shut-off valve is working

The other likely offender of constant drainage is a broken auto shut-off valve.

The purpose of an ASO valve is to shut off water to the filters and membrane once the storage tank is at full capacity.

In case of a malfunction or damage to the ASO valve, this will cause water to keep draining as it has nowhere else to go.

The solution to this problem is to replace the broken ASO valve with a new one as quickly as possible.

3. Inspect check valve for damage

The check valve and ASO valve are instrumental in regulating pressure inside your RO unit.

Failure of any one of these valves can result in continuous draining of water.

The main purpose of a check valve is to shut down the unit once the storage tank is full.

For the check valve to shut off it would require a minimum of 40 PSI of water pressure from your municipal water supply.

If the water pressure is lower than that this could be the reason why your RO system is constantly draining as the check valve won’t shut off.

However, if the PSI level is 40 or higher and the check valve still fails to shut off water to the membrane this means that the check valve is most definitely broken and should be replaced immediately.

4. Check for any ruptures or damage to the air bladder

An air bladder can be damaged in cases of extreme water pressure or lack of maintenance.

A damaged air bladder won’t be able to produce or maintain enough pressure inside the RO system. This will result in very little or no water coming from your faucet.

To easiest way to check if the air bladder of your RO unit is damaged is to add a glass of water into the tank at normal pressure.

If the water still barely trickles out from your faucet your air bladder is definitely damaged.

Unfortunately, this is very bad news, as air bladders can’t be repaired or fixed. The only option is to buy and install a new RO unit. Ouch!

5. Look for signs of wear & tear on the flow restrictor

The flow restrictor is what controls when and how much water is to be drained from the tank.

A worn-out flow restrictor will allow a lot more water to flow through the drainage pipes, creating noise and causing a lot of water wastage.

A broken flow restrictor will also reduce the pressure inside your reverse osmosis unit leading to further issues.

As such, it is highly recommended to replace the flow restrictor on your RO unit annually along with the filters.

6. Check the RO membrane

If your RO system isn’t producing any more water or the flow of water from the faucet is much lower than normal this is an indication that your membrane needs replacement.

A clogged membrane will also cause water to flow directly into the drainpipe without ever reaching the tank. As a result, your reverse osmosis unit is not producing any water.

You can flush out the membrane yourself but if it needs replacement, it is best to call in a water treatment expert to get the job done.

Learn how to replace the reverse osmosis membranes in my article.

Frequently Asked Questions

Q) What is the normal drain time for an RO unit?

When an RO unit is filling the storage tank you can expect water to keep draining. However, after a couple of hours of no use, there shouldn’t be even a drop of water going to the drain. If you still hear water draining, you likely have one of the issues listed above.

Q) How often should I clean or flush the membrane on my RO unit?

The membrane is what holds all the impurities and residue that you don’t want in your water. As such, a membrane should be sanitized, flushed, and/or replaced on a regular basis to ensure there are no clogs or blockages.

Q) How to add air to your RO storage tank

In some instances, the air pressure in your storage tank can be too low. To increase the pressure in the tank simply use a bicycle pump and use a pressure gauge to measure the PSI to the desired level. The air valve on an RO tank is the same valve that is used on a bike tire.

Final Thoughts

RO systems are complicated devices and as such require constant maintenance and care. If at any time you feel the problem at hand is beyond your comprehension, call an expert rather than trying to fix things on your own. You can likely do more harm than good.

Chief Guru

Richard Boch is a chemical engineer responsible for designing water filtration systems for industrial and residential customers. He has more than 20 years of experience with ion exchange, activated carbon, and reverse osmosis. Richard's expertise has made him a go-to source for municipalities and businesses looking to improve their water quality. When he's not working, Richard enjoys spending time with his wife and two young children. You can also follow him on LinkedIn, Twitter and Facebook.

Recent Posts