What is an Air Gap Faucet?

By a show of hands, who knows what an air gap faucet is?  Who knows what reverse osmosis is, or a reverse osmosis unit?

This post will explore the answers to these questions and help you become conversant in new faucet lingo for chats with your plumber or reviews of plumbing codes as they relate to air gap faucets.

Simply stated, if not exactly clearly so, an air gap faucet has an air gap (well, no surprise there) built into the base of the faucet.  You can get water from an air gap faucet just as you can with a non-air gap faucet – turn the water on, you get h2O.

Let’s get into the details, though, for that clearer understanding.

What is The Purpose of An Air Gap Faucet?

Before we can answer this question, we need to talk about reverse osmosis first.  Reverse osmosis is a process for purifying water by passing it through a semipermeable membrane (some things allowed to pass, others filtered out) that removes things you don’t want in the water you drink or use for cooking.

Here’s a good video that explains and shows this process.

Another term for an air gap faucet is a reverse osmosis (RO) faucet.  Under the sink, water filtration systems come with an RO faucet, although you can also purchase an RO faucet on its own. 

They are designed to prevent backflow into a reverse osmosis system using an air gap and direct the water down the drain. 

Imagine water from the supply line passing through the filter, called for when you turn the water on at the faucet, but not using all of the water that has already passed through the filter.  That water has to go somewhere but not back into the filter.

The air gap RO faucet is an essential part of the reverse osmosis drainage system.  The air gap device keeps the filtered but unused water flowing in the right direction – down the drainpipe with other waste water.  Water can not climb air, but it can climb up a pipe.  The air gap prevents the unused water from climbing back into the RO system.

What is The Difference Between Air Gap and Air Break?

From a plumber’s perspective, there is a difference between an air gap and an air break.  They are used in different plumbing scenarios but for the same purpose: to prevent water from going where it shouldn’t go.

An air break usually refers specifically to drainage, whereas an air gap has more to do with water supply.  An air break would be found when a drainage pipe from one space to another discharges water into a hub drain (one into which several lines drain). 

Each of those pipes would drain into the “air” and then into the main hub drain to be carried away.  The air break would prevent backup through the several pipes into the rooms they were draining from, such as a locker room shower, or a cold room, because water can’t climb air.

An air gap refers to drainage away from an appliance or fixture, and in our case, it is the filtration unit.  It ensures the water goes to the right pipe (the downward drain)  without crossover returns to the RO device.

These terms are sometimes used interchangeably, but there really is a difference.  For our purposes today, we are referring to an air gap.

Should Water Come Out of The Air Gap?

The short answer is no, not on a regular basis. 

When an air gap leaks, it will often be caused by an obstruction in the tube that runs from the air gap to the drain pipe under the sink.  Curing may require cleaning the air gap. 

It might also suggest the drain line below the sink is clogged and in need of being cleared.  If you have a garbage disposal, you might want to run it just to see if it is contributing to leakage from lack of use.

Water coming out of the air gap is not normal.  Check these likely cause spots as part of your troubleshooting protocol and take appropriate action to correct them.

How Do You Clean an Air Gap?

Speaking of cleaning an air gap, you might be wondering how.  Materials may accumulate in the air gap, creating a clog that will cause leakage.  There is actually an air gap cleaning brush tool for the purpose.

If you can see any material that may have gathered in the air gap after removing the cap for visual inspection, perhaps you can remove it with your fingers.  But, if you can’t, a cleaning brush specifically for this purpose will do the job, also. 

You can purchase an air gap cleaning brush tool at a plumbing supply store, one of the major DIY stores, and online.  For those of you who remember baby bottle cleaning brushes, the brushes made for cleaning air gaps are similar, only thinner and longer upwards of two feet long.

Final Question:  Do You Need an Air Gap For Your Kitchen Faucet?

Most plumbing codes require an air gap for use with an RO system.  As explained above, it is an essential part of the RO system drainage and helps prevent contamination of already filtered water. 

RO systems facilitate filtered water flow through their own faucet, and manufacturers most often choose to use a faucet with an air gap already inherent in the faucet.

So, the answer is yes; you do need an air gap for your kitchen faucet if you’re under the sink; the water supply includes an RO system.  This is so whether your local plumbing code requires it or not, as it is integral to a clean and pure overall filtration system and ensures that water goes in the right direction.

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