What is this pipe-connection for?
September 20, 2014 1:11 PM   Subscribe

In my new airing-cupboard, there is a pipe-connection that looks very odd. Photo here. My initial thought was that something had corroded, but the cut-out areas are identical on each site, and look like they're supposed to be there. Is this right, or should I be getting someone to fix it? If it's supposed to be like this, then why? And should water be dripping from the top-pipe into the bottom?
posted by gregjones to Home & Garden (4 answers total) 1 user marked this as a favorite
That's an air gap to prevent suction from drawing material up the pipe. Without more data we can't tell whether it should be there but that's what it is.
posted by BrooksCooper at 1:13 PM on September 20, 2014

Best answer: It's an air gap, for sure.
The bottom pipe empties into a drain, right? Probably upstream of a trap, or does it lead directly outdoors?
Where does the top pipe go?

The top pipe could be the condensate line from your air conditioner, or from a high-efficiency flue-gas-condensing heater or boiler, or perhaps a de-humidifier (looking at your weather today).

An "airing cupboard", so you have a water heater in there, or other appliance that consumes energy and makes heat? A high efficiency water heater would also have a condensate line.
posted by the Real Dan at 1:42 PM on September 20, 2014

I heard them called gap drains.
posted by JujuB at 5:56 PM on September 20, 2014

Best answer: It's supposed to be like that (but could probably stand to be be cleaned up a bit.)

Whether or not it should be dripping: it depends. If it's a condensate drain like the Real Dan suggests, then yes, it's supposed to do that.

If it's the tell-tale drain downstream of a hot water heater pressure relief valve or something like that, then no; it would indicate the valve is leaking by. I would think, though, that in that case the bottom pipe would have a bigger funnel shape to catch the momentary blast from the valve lifting. And even if that's what it is, it's not that big of a deal as long as the valve still works.

The pressure relief valve is usually at the top of the hot water heater and has a little lever on it to manually lift the valve. Sometimes if the valve is leaking by, exercising the valve a couple of times with the manual lever flushes it out and lets it re-seat properly.
posted by ctmf at 6:10 PM on September 20, 2014

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