I recently bought a house and have a slight leak under my kitchen sink. Was trying to figure out where it was coming from this morning so I could fix it, when I found something that makes no sense to me.

There is a filtered water dispenser on sink, on the right here which has two drainage lines coming out of it underneath here that feed into the drainage pipe from the dishwasher here

I'm really confused by this. I don't understand why it would need one drainage line, let alone two. What am I missing here?

  • It's. A filter, right? It removes crud from water, right? Where would the crud go? – Harper - Reinstate Monica Jan 26 at 18:17
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    No, that's just the spigot. The blue line is the inlet from the filter. Also, the crud stays in the filter which you have to replace occasionally – Kevin Jan 26 at 18:30

I found a good explanation at: http://www.purewateroccasional.net/hwairgapfaucet.html

The filter (possibly Reverse Osmosis) part has a drain pipe. But it doesn't go directly to the drain. Goes up to the tap base, where it dribbles in the open air (the "air gap") and back down through the other pipe to drain away.

If the second drain line becomes blocked, this "air gap" can leak. Not sure if the possible leak would only occur when the tap is in use.

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    The first RO I ran into the home owner was complaining of low water pressure and high water bill , the water out of the normal tap was horrible but the RO was awesome, it used a lot of water but was really good I think it was a 5 to 1 ratio for each gallon of good filtered water it took 5 gallons to make plus a small constant drip, that is a smaller unit than I have seen but makes sense.+ – Ed Beal Jan 27 at 5:12
  • But they both go down the drain. Maybe there was originally a Reverse Osmosis filter, but it was replaced by a standard filter and they just cut the drain line from filter to tap and shoved it in the drainage as well??? – Kevin Jan 27 at 17:12

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