A non-air gap RO faucet is a standard RO faucet with only the pure water line/tube connected to it as opposed to the three lines in air-gap RO faucets.
The drain line, in this case, is connected directly to the under the sink drain pipe. Therefore, with a non-air gap faucet, the wastewater from the RO membrane is routed and emptied directly into the sink line without going through the faucet.
The faucet usually uses 3/8” tubing for the pure water from the RO membrane to the faucet and a ¼” drain tubing which delivers the wastewater from the RO membrane to the sink drain. It requires around ½” to 5/8” hole for installation on the sink or countertop.
Advantage of using a non-air gap RO faucet
The first thing to like about the non-air gap RO faucets is the fact that they are very straightforward when it comes to installation.
Unlike air gap faucets, these have fewer connections and tubing as it’s only one water line that needs to go up to the faucet hence allowing for easier and faster installation.
Another commendable thing about the non-air gap RO faucets is that the drain line coming from the RO system goes directly into the sink drain pipe. Therefore, there is no gurgling sound which often occurs in the air gap faucet as the drain water passes over the faucet base and drops into the drain line tube that flows into the sink drain line.
Without the additional parts and connections, non-air gap faucets generally tend to be much less expensive too compared to most air gap faucets which makes them a good replacement option for those in a budget or don’t wish to install an air gap system.
Disadvantages of a non-air gap RO faucet
While air gap RO faucets provide ample protection to your RO system against the backflow of wastewater, non-air gap RO faucets, on the other hand, don’t offer such protection.
If the sink drain gets clogged or backs up, then chances of the wastewater flowing back to the RO system are high which could end up damaging the system or contaminating the RO membrane.
The other major setback of non-air gap RO faucets is that they are often considered non-compliant for most local plumbing codes since many of them require RO systems to be installed with air gap faucets.
Furthermore, while air gap faucets can work with both a non-air gap and air gap RO system, non-air gap faucets can only work with non-air gap systems which kind of limits your ability to customize your RO system in case your building code requires an air gap system.