An air gap RO faucet is a faucet that has an “air gap” installed in the RO system drain line which creates a siphon break from the RO system itself and the sink drain.
The main reason behind the air gap design is to prevent any back-flow of water from your kitchen sink drain into your RO system via the drain line connection.
How does it work?
The air gap RO faucet accomplishes this by routing the drain line water discharged by the RO membrane upwards to the base of the faucet where it falls into a small, non-pressurized trough, rather than directly into the sink drain pipe.
The water then passes over to the other side inside the faucet stem where it then drops into a 3/8” flexible tube by force gravity and flows to the sink drain. Therefore, the wastewater from the RO membrane flows out of the system from one tube into another via the air gap.
Therefore, in case the sink drain is clogged and backed up, then the air gap in the RO drain line would pull only a small amount of air back into your RO unit instead of the dirty water.
On that note, the air gap faucet requires three tubes than one which is what a standard faucet requires to operate. One is ¼” inlet tube for routing the drain water from the RO membrane upwards to the faucet.
The second one is a 3/8” outlet tube for routing the drain water downwards to the sink drain, and the final one is ¼” pure water line for delivering the purified water to the faucet, which you drink.
All these tubes are normally color-coded (red, black, and blue), so you won’t have a problem getting a hang of what connects to what.
Benefits of installing an air gap RO faucet
There are quite a number of advantages to installing an air gap RO faucet.
The first one is that it offers great protection to the RO system. The air-gap system ensures that only a small amount of air gets siphoned back into your RO system.
No dirty water would flow back into the discharge line of your RO system which could damage the water lines and the unit as well as contaminate the membrane.
An air gap faucet simply offers an easy way to safeguard your RO system against future plumbing issues.
The local plumbing codes in many areas makes it mandatory to use an air gap faucet with a reverse osmosis system. However, the best part about air-gap RO faucets is that they can work with either air gap or non-air-gap RO systems.
If you live somewhere the plumbing regulations don’t require it, then you may not need to install it or you can even install an external airgap which fits around the RO faucet. You can also use a combination of dishwasher and RO system airgap.
While the air gap RO faucet has several benefits, nothing is perfect. It does have some downsides which include:
The air gap RO faucet has small tubing and the water in the trough is non-pressurized.
Therefore, even a small piece of sediment or food lodged in the drain connection inlet or the small hole in the faucet can cause clogging leading to the drain water flowing back up into the sink or countertop.
A bit Noisy
RO systems are generally quiet, however, they can also be a bit noisy especially with the air gap system installed. It may make a gurgling sound as the wastewater is pushed from the RO membrane to the drain.
You might as well hear additional gurgling sounds as the storage tank is slowly getting filled with water.
Not Ease to Install
Air gap faucets are a little more complicated to install compared to a standard faucet. To start, they require three tubes to connect as opposed to just one which makes the installation cumbersome.
In addition to that, the air gap faucet usually requires a larger counter hole than a standard faucet. You need to drill around 1½” opening which requires some good skills to ensure you do right, especially if you are to drill the hole through the countertop.
However, once you are done with the hole, the remaining installation is pretty much straightforward.
How to install an air-gap RO faucet
This video will show you step-by-step on how to install an air-gap RO faucet.
You can learn more about the whole RO system installation here.