Reverse Osmosis Faucet Leaking from Air Gap? Here’s What to Do

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Air gap faucets are commonly used with reverse osmosis systems for their ability to prevent wastewater backflow into the RO membrane.

While they work well at this, they tend to clog up and leak – so you’ll want to familiarize yourself with their operation and potential leak causes.

Let’s take a look at some of the most common reasons for why a reverse osmosis faucet could be leaking from its air gap, and how you can fix these issues yourself.

Key Takeaways

  • Air gap reverse osmosis faucets are faucets with built-in backflow protection to protect the filters and RO membrane from wastewater. These faucets perform well at this task, but they do tend to clog and leak.
  • The design of an air gap faucet means there is a small opening in the faucet which can leak if the drain line is clogged or otherwise obstructed. A loose drain saddle, improper installation of the drain saddle or faucet, system wear and tear, and high-pressure feed water can also cause this problem.
  • A clogged drain line needs to be cleaned. Remove any kinks or dips as well. Tighten a loose drain saddle and other system connections. Make sure all components are installed correctly and that incoming water pressure is within reasonable limits. A worn-out RO system may need replacement.

How Does an Air Gap RO Faucet Work?

An air gap RO faucet is a faucet with built-in backflow protection to prevent wastewater from flowing back into the filter system should the sink drain pipe become clogged. Air gap faucets are often sold with RO systems – and are even required by plumbing codes in some municipalities.

Unlike a regular reverse osmosis faucet – which only has a single connection from the post-filter to the faucet, an air gap faucet has three tubing connections.

  1. Like a typical RO faucet, an air gap faucet has a connection running from the final filter stage to the filtered water inlet.
  2. Another connection runs from the RO membrane outlet to the faucet stem. This line carries wastewater to the faucet and passes it by an air gap (which is a literal hole in the faucet fixture).
  3. Then after the wastewater passes by the air gap, it flows to another drain line running down to the drain saddle attached to your sink’s drain pipe.

young girl opening reverse osmosis faucet

Why Does a Reverse Osmosis Faucet Leak from the Air Gap? + How to Fix

There are several reasons your reverse osmosis faucet might be leaking from the air gap.

Of course, the purpose of an air gap RO faucet is to prevent wastewater backflow into the system, so if the faucet is leaking at least you’ll know the air gap is working as intended.

A Blockage in the Drain Line

A common reason for water leaking from the air gap is some type of blockage in the drain line. This can happen when a large piece of debris obstructs the flow of water down the line – the water has no other place to go than to flow out of the air gap.

Another possibility is the drain saddle has come loose and is blocking or pinching the drain line. This can block the flow of wastewater down the drain as well – which again will cause water to leak out the air gap.


If you suspect that a clogged drain line is the cause, the first thing to do is disconnect the drain line from both the barb on the faucet and the drain saddle. Then, manually clear the line with a pipe cleaner to break up the obstruction.

If there is no clog in the drain line, then take a look at the drain saddle mounted to the drain pipe. If it’s loose, it can pinch off the drain line causing a clog. Realign the saddle with the hole in the drain pipe and then fasten it tight. You can insert a pen or screwdriver through the saddle and hole to ensure they’re properly aligned.

Another possibility is that the stem attached to the faucet is damaged. Take a look at the stem to check for damage. If this is the case, you’ll need to replace the faucet entirely.

A Kink or Dip in the Drain Line

Another common issue is a kink or dip in the drain line. As reverse osmosis systems are fairly low pressure, this can be enough to stop the flow of wastewater and push it to the air gap.

This should be fairly easy to spot by taking a look at the drain line. Obvious kinks in the line are easy to spot, while a dip in the drain line below the drain saddle may not look like a blockage but it can cause backflow toward the air gap.


The obvious solution here is to straighten out the line and remove any possible kinks.

If the drain line dips below the drain saddle, then you’ll want to cut the line shorter so that there is no excess line. Then reattach it and test the flow by turning on the faucet.

Reverse Osmosis System Not Installed Correctly

Another possibility is that the RO system – specifically the faucet and the drain saddle – was not installed correctly in the first place. This is less likely in the case of a professionally installed system, but a DIY install can lead to all sorts of issues if done incorrectly.

The first thing to examine is the positioning of the drain saddle. Drain saddles should be installed above the P-trap and far away from the dishwasher drain hose and/or garbage disposal. These connections can shoot debris into the drain pipe, which can clog up the RO system’s drain line.

Air gap RO faucets can also be installed or hooked up incorrectly, so you’ll want to take a close look at the faucet and insure it was installed per the manufacturer’s instructions.


If the drain saddle was installed improperly, then you’ll need to remove it and reinstall it in the correct location. This will also require replacing the section of drain pipe where the saddle was previously installed.

If the faucet is improperly installed, then you may need to reinstall it in a new location. If the tubing connections are improperly hooked up, the solution is relatively easy – simply connect the tubing as per the manufacturer’s instructions.

A Loose Connection

A loose connection somewhere in your RO system is another cause of your RO system leaking. This typically happens to newly installed units, as it’s fairly easy to install a tube connection loosely the first time.


This issue can be fairly easy to fix as you might be able to spot the loose connection from the water seeping from it.

Identify the loose connection and tighten it.

plumber installing reverse osmosis system under sink

Wear and Tear

Like any other mechanical system, reverse osmosis systems will age and break down over time. The typical RO lifespan is between 8 and 10 years, so if your system is reaching that age there is a good chance that your system will start to form leaks and other problems.

Leaks can form from several different areas, including the air gap in the faucet.


If your reverse osmosis system is reaching the end of its lifespan, the only real solution is replacing the entire system with a new one. Consult your manufacturer’s instructions to confirm the system’s lifespan and replacement schedule.

Feed Water Pressure Too High or Pressure Spikes

Occasionally, excessive feed water pressure or spikes in water pressure can cause damage to the connectors, tubing, or drain line. RO systems are designed to work within a certain pressure range for the RO membrane to function correctly so excessive pressure can be an issue for the overall system as well.


If you’re dealing with consistently high internal pressure then you’ll want to consider installing a pressure regulator. This will lower the pressure to the ideal level for your reverse osmosis system to run optimally.

How Can You Prevent Your Air Gap Reverse Osmosis Faucet from Leaking Again?

Leaking from the air gap faucet is not necessarily a bad thing – as it’s an indication that the system is working as intended (more or less). However, it’s a bit of a pain to deal with, so you’ll want to take steps to ensure the faucet won’t leak excessively.

There are several precautions you can take in order to reduce to reduce the chance of leaking. Mostly, you want to ensure the system is correctly installed, the connections are tight and not leaking, there are no kinks or dips in the drain line, and there’s no blockage preventing the drain line from flowing.

If you have any questions about your reverse osmosis leaking from the air gap please don’t hesitate to leave a comment below!

About the Author Gene Fitzgerald

Gene Fitzgerald is one of the founders of BOS and currently head of content creation. She has 8+ years of experience as a water treatment specialist under her belt making her our senior scientist. Outside of BOS, Gene loves reading books on philosophy & social issues, making music, and hiking.
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Leave a Comment:

Jeff Harker says March 6, 2023

We installed a WaterMaker 5 at a customer’s house and water sputters from the air gap when the sink stopper is pushed in with a little force or if the sink was filled with with water. It sounds like a venting issue or something. The kitchen sink drains fine but it seems like air is getting forced up the R.O. faucet’s waste water line forcing water to sputter from the air gap hole. Everything is connected correctly, and we made sure all lines were free of any blockages. I was just curious of you have run into this issue.

Thanks and Regards,

Jeff Harker

    Gene says March 9, 2023

    Sorry Jeff, never had this issue before, and I’m not sure what’s causing it.

Beverly Ciavarella says February 20, 2024

I had my reverse osmosis water system installed by a plumber a few weeks ago. Worked fine for first couple weeks, however on the shut of valve on counter the side has a slit on it where water runs out. Is a replacement piece available?

    Gene says February 21, 2024

    Hi Beverly,
    Can you give us the exact model?

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