Reverse Osmosis System Leaking Under Sink? Here’s What to Do!

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If your reverse osmosis system is leaking under the sink, we understand how inconvenienced you feel.

But don’t worry; this article will show you what to do if your under sink reverse osmosis system is causing issues.

We’ll also give you some tips to prevent future leaks. Let’s go!

Key Takeaways

These are the common causes of leaking under sink reverse osmosis systems and what to do about them:

  • Over-tightening a filter housing can cause irreversible damage. You’ll have to change any cracked parts.
  • Tighten all loose connections with a wrench. Besides, make sure that push-fittings are pushed all the way in. If the leak persists, change any broken fittings or adapters.
  • Replace any clogged filter cartridges.
  • Replace any damaged parts of the RO tank. If that’s not possible, buy a new tank.
  • Reduce feed water pressure if too high (check product manual).
  • Completely replace an old under sink RO system that has reached the end of its life.
  • Avoid low quality RO units and replacement filters.

How to Troubleshoot a Reverse Osmosis System Leaking Under the Sink

Identifying the source of the leak is the first step to fixing it. Your under sink reverse osmosis system might be leaking for various reasons. They include the following:

  • Too loose or too tight filter housing
  • Incorrect installation
  • Damage from hot water
  • A bad O-ring
  • Sediment building up on an O-ring channel
  • Loose valve
  • A sudden spike in water pressure

Where Is the Water Coming From?

Noticing a pool of water under your kitchen sink can be jarring, but you can easily find out where the water is coming from and stop the leak.

To find the source of the leak, grab a flashlight (your phone’s torch also works) and inspect the area under the sink around your RO system. Possible places the water might be coming from include:

  • Tubing connections
  • Filter housings
  • Pressure release buttons
  • The RO faucet
  • The water storage tank

Under Sink Reverse Osmosis System

Why Your Under sink RO System Might Be Leaking

There are multiple reasons for why your under sink reverse osmosis system might be leaking. We’ve discussed them below including how to fix them.

Loose Tubing or Other Connection

Connections can get loose over time due to regular wear and tear. Loose tubing or connections cause leaks to spring up in the RO system.

Accidental bumping is a very common cause of loose connections, too. Since under sink RO systems are usually located in cabinets, someone might accidentally tug a line or bump the system whenever they’re accessing that cabinet. This accidental bumping could cause loose connections and leakages.

Another way you can get loose connections is if there was a mistake during installation or if there’s an incompatible adapter.


The solution here is to tighten the connection. You can do this yourself using a basic wrench.

Remember to push the tubing all the way in if it’s a quick-connect fitting.

If the water continues to leak after you’ve tightened a connection, you’ll have to change the fitting or adapter.

Over-Tightened Filter Housing

A lot of times, an over-tightened filter housing is the cause of an under sink RO water filter leaking. If the canister is overly tightened, hairline cracks can start to form on the threads or in the sump, causing leakage.

An over-tightened filter housing can also crush the O-ring, leading to serious leakage.


  • Replace the O-ring if it’s damaged
  • Buy a new filter housing if the old is cracked or damaged.

Clogged Filter Element

Clogged/worn-out filters slow the filtration process and restrict water from flowing freely. If at some point water pressure gets too high, it might cause a dripping leak at one of the connections or a full burst.


Depending on your water usage and quality, you’ll need to replace your filters more frequently. This definitely applies if you have hard water.

Alternatively, you could protect your filters from hard water by installing a water softener at the point of entry to your house.

A Damaged Water Storage Tank

A damaged storage tank could also cause leaks. For example,

  • the air bladder inside could be torn,
  • there could be a hole in the tank,
  • or one of the valves could be malfunctioning.


Locate and replace any broken parts, or buy a new tank.

Issues with Feed Water Pressure

If feed water pressure is too high or unstable, it could lead to issues like membrane shell rupture, which again can cause leaks.


Check your home’s water pressure and adjust it if necessary (and possible).

You could also install a separate pressure valve before your under sink reverse osmosis system.

Overall Age of Your RO System

The older your RO system, the more susceptible it is to problems like leaks. The lifespan of a properly maintained RO system is around 10 years. Since RO systems are highly pressurized, the constant wear and tear over time can cause them to develop leaks.


Service your system regularly (every six months) and keep track of its age. Once your system is around the 10-year mark, and the issues become more intense, you’ll need to get a new one.

Low-Quality Product

Buying a low-quality RO system could result in repeated issues with leaks from the start.

Using low-quality replacement filters can also be problematic.


Only buy products from reputable brands with top-grade quality.

Tips for Preventing Future Leaks

It’s one thing to fix leaks, and it’s another to prevent future leaks from happening in your under sink RO system. We’ve discussed some ways you can avoid future leaks below:

Use High-Quality Components Only

As mentioned before, only use high-quality filter cartridges when you maintain your RO unit. Low-quality filters clog quickly causing leaks.

Replace Filters in Due Time

Our second tip for preventing future leaks: Replace pre and post-filters as well as the RO membrane in due time (check manufacturer specifications). This will lower the chances of running a clogged filter cartridge significantly.

Different Water Filter Cartridges and Membranes

Be Careful When Replacing Filters

When replacing filters, some people tend to over-tighten the filter housing—be careful not to do that. Only tighten the filter housing with the plastic wrench provided or with your bare hands. This will prevent the sump housing from getting cracked.

Inspect and Clean Your Under Sink Reverse Osmosis System Regularly

Cleaning your under sink reverse osmosis system regularly is essential to keeping it in good shape. Fortunately, you don’t need any fancy cleaning gear or complicated cleaning routine. Cleaning your system twice a year with dishwater and a sponge is enough to remove the buildup of dirt and sediment.

Also, remember to clean and lubricate all O-rings. Faulty O-rings cause most leaks in under sink RO systems, so you have to be on the lookout for that.

Note: Never lubricate the O-ring with petroleum jelly. Only use silicone-based lubricants.

Lastly, check your under sink system weekly to ensure everything is working fine. Confirm that the storage tank is in good condition, and replace your filters quickly if your water starts to taste different.

If you have any questions about reverse osmosis leaking under sink please don’t hesitate to leave a comment below!

About the Author Alexandra Uta

Alex is a content writer with an affinity for research and a methodical attention to detail. Since 2020, she has fully immersed herself into the home water treatment industry only to become an expert herself. Alex has been using water filters and similar products for years which has gained her lots of hands-on experience.
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