Reverse osmosis faucets come in two forms and the difference is not cosmetic. An air gap faucet carries the system's drain line up through the faucet body, across a physical gap, and back down to the waste connection. A non air gap faucet is a plain tap and the drain line runs directly to the waste. Which you should fit is decided by plumbing code and by what your drain arrangement is.
What the air gap does
It is a backflow barrier. The reject line from the system rises inside the faucet body, discharges across an open gap into a second channel, and flows down to the drain saddle. Because the two sides never physically connect, no blockage or pressure event in the waste pipe can push water back up into the reverse osmosis system and, from there, towards drinking water. It is the same principle as the gap between a tap spout and the rim of a basin, applied to a small drain line.
Why plumbing codes ask for it
Many jurisdictions require an air gap on a reverse osmosis drain connection precisely because the alternative relies on the drain never backing up. Requirements vary by location and are worth checking before buying a faucet, since fitting the wrong one means changing the tap rather than adjusting a pipe. Where an air gap is required, some installers instead use an approved air gap device fitted in the drain line rather than in the faucet, which satisfies the requirement while allowing a plainer tap.
Why installers often dislike them
Air gap faucets have a reputation, and it is partly earned. They are noisier, since water crossing the gap gurgles audibly during production. They need a larger hole in the worktop or sink deck because of the extra channels. And the gap can spit or overflow onto the counter if the drain line downstream becomes partially blocked, which is exactly what the design is meant to reveal but is unpleasant when it happens. A blocked outlet channel is the most common service call on these faucets.
Choosing and keeping it working
Check the local requirement first, then the hole size in your sink deck, then decide. If an air gap is required and you dislike the faucet type, ask about an in line air gap device. Whichever you fit, keep the drain saddle clear and correctly positioned above the trap, since most air gap complaints trace to a restricted line downstream rather than to the faucet. If water appears at the gap, clean the drain line before assuming the tap is faulty. Our filtered tap guide covers the fixture options.
Questions people ask about ro faucet with air gap
What does the air gap on an RO faucet do?
It creates a physical break in the drain line so nothing can siphon back from the waste pipe towards the system and the drinking water.
Is an air gap faucet required?
In many jurisdictions, yes, for the reverse osmosis drain connection. Requirements vary, so check locally before buying the tap.
Why does my air gap faucet gurgle?
Water crossing the open gap is audible during production. It is normal, though a loud change can indicate a restricted drain line.
Water is spitting out of the gap. What is wrong?
Almost always a partially blocked drain line or saddle downstream. Clear it before assuming the faucet itself has failed.