I recently replaced my RO filter system with a simpler water filter system. I did not get a new faucet since I figured that I could just use the existing one that was installed with my RO system. Once I started tinkering around, I discovered the 2 extra drain hoses on my RO faucet (an air gap faucet). The faucet looks like this: https://www.freedrinkingwater.com/support/wp-content/uploads/all-ro-faucet-installation-figure1.jpg

Referencing the image, I disconnected the orange line and just left it uncapped under my sink. I left the black line to the drain saddle where it was. I plugged my new clean water line where the blue line is in the above image.

As I understand the 2 drain lines in the air gap faucet just connect to each other inside the faucet and to a vent hole in the faucet base.

Is this a bad idea? Are there any possible problems I should be aware of? I'd rather not replace the faucet because it's in a really tight spot that's hard to access. Any insight would be appreciated.

  • Problems with your terminology. An air gap is not a faucet, do you mean a faucet that is put in the hole intended for an air gap ? If you could post the model number AND PHOTOS it would help to understand the mechanics of your system. Regular faucets do not have drain lines so i am not sure what you are talking about.
    – Alaska Man
    Jun 14, 2019 at 16:55
  • @AlaskaMan, some filter systems use a special faucet with 3 hoses, like this. OP is under the impression that the extra two lines are for some vent or air gap. I've never installed one and don't know what the extra tubes are for (he could be right).
    – JPhi1618
    Jun 14, 2019 at 17:46
  • @AlaskaMan: Hi, I updated my post w/ an image. Hopefully, you'll have a better idea of what I'm trying to describe. Incidentally, I only assumed the term for this type of faucet was called "air-gap" because of this source: freedrinkingwater.com/support/troubleshooting/air-gap-faucet
    – awei
    Jun 14, 2019 at 20:00

1 Answer 1


I think the air gap in an air gap faucet is separate, mechanically speaking, from the actual faucet. It's just in the same mechanism because both need to be in a similar physical location. Leaving both the drain and waste lines disconnected should be appropriate, and shouldn't give you any surprises.

To expand on that:

The air gap in a RO system exists because it needs to flush itself with water to clean up every so often. That water is waste water, and is not drinking quality. So, it goes down the drain. The air gap has the same purpose as on a dishwasher; to ensure that any blockages result in water overflowing into the sink instead of backing up or damaging any equipment. (Note the overflow hole in the faucet.) Because this mechanism relies on gravity, it needs to be placed above the level of the drain. None of this interacts with the actual faucet, but the faucet also goes next to the sink, so you might as well reuse the hole. You could have a dishwasher-style air gap and a regular faucet, and that would also work.


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