Plumbing vented inside apartment? Is that OK?
August 28, 2011 2:24 PM   Subscribe

We moved into a new rental last month and after we moved in I notice some unusual plumbing.

The kitchen sink drain pipe goes into the wall and comes out the other side in a pantry before exiting through the floor. The weird thing is that it also vents directly into the pantry from the soil pipe. There's no valve of any kind on the pipe, it's just cut and left open. Here's a picture.

I don't have a great understanding of plumbing, but I thought that everything needed to be vented to the outside, and that venting any kind of plumbing inside is bad (health risks, pest risks, odors, fire, etc). I can't find anything specific online that will confirm how serious an issue this is in a specific way, only that this is not the right way to do it.

Plumbing experts: if this is no big deal, let me know (that'd be great). But if it is a bad thing, can you point my to some plumbing code (I'm in CA) or any reference material that I can use to motivate my property manager to address it? I've rented from him for years (in another building, just moved into this one) and he's great about taking care of little things but stuff like this needs serious prodding.

Details: 1908 building, I'm on the second of four floors but not sure of what kind of plumbing is above or below mine (but I do know that the layouts are different from my unit). Thanks.
posted by quarterframer to Home & Garden (10 answers total)
The 'U' trap under each sink prevents sewer gas from coming back in to your fixtures; the vent in your picture is meant to prevent build-up of sewer gas pressure, and really needs to be outside.

Sewer gas is noxious and flammable (somewhat). This definitely isn't code - at least not where I live (NJ) - and your landlord should fix this ASAP for you.

Of course, this assumes that the pipe is still functional and not just a lazy unused leftover from a previous renovation.
posted by bfu at 2:36 PM on August 28, 2011

At the very least, this is bad practice. If there's a trap below the floor, and the top of the pipe is above any other drain in the house, then you'll not likely have any problems. It'll just be an ugly plumbing hack. If there is no trap below the floor, you may have stinky sewer gases bellow into the room, which is not only unpleasant, but can be dangerous. Also, if the opening is lower than other drains tied to the same line, if the main gets backed up, it may back up and overflow this vent. I'd make the landlord aware of this problem.
posted by 2N2222 at 2:36 PM on August 28, 2011

With the p-trap in it like there is and given its height, I'm inclined to think that that was once a standpipe for a washing machine and not intended as a vent. I'd say duct tape off the top hole and see if the sink drains without issue. If so, cap that off with a 1-1/2" (guessing) cap and pipe cement.
posted by humboldt32 at 2:44 PM on August 28, 2011

humboldt32, that is quite possible. There are ancient, painted over washing machine hookups back there. Do I run any risk of dmaging anything by trying the duct tape test?
posted by quarterframer at 2:54 PM on August 28, 2011

Nope. Give it a go.

You could alternatively pour a pitcher of water into that standpipe so that the P-trap fills with water. Then see if it gurgles at all when running water down the kitchen sink. Same test basically.
posted by humboldt32 at 3:05 PM on August 28, 2011 [1 favorite]

What you might want is an air admittance valve. This is a one-way valve that allows air into the pipe if a vacuum develops as water drains through the pipe, but otherwise stays closed so that gasses can't escape. Venting outside is better, but these valves are made for situations where venting outside isn't feasible.
posted by jon1270 at 3:12 PM on August 28, 2011

There are ancient, painted over washing machine hookups back there.

Definitely for the old washing machine drain. Rather than duct tape, I would rubber band or tape around a piece of plastic bag over the hole. Duct tape decays and will come off leaving a sticky residue.
posted by at 4:13 PM on August 28, 2011

I meant to remove the duct tape after the test and cap it off properly with a pipe fitting.
posted by humboldt32 at 4:55 PM on August 28, 2011

jon1270 has nailed it.

You have to have a vent, and that is what that pipe is doing, or else the trap in the sink
will siphon itself dry and allow sewer gas into your house. But since the vent opens into
your house, it will admit sewer gasses itself.

The air-admittance valve of which he speaks is up-to-code, in some parts of the country,
and is absolutely the best thing to do. The air-admittance valve is not code in my county
of California, but don't tell anyone, and you'll be fine.

If you seal that pipe, then your sink might not drain well (glug, glug, glug), or it might just
siphon itself dry on each use (stink, stink, stink).
posted by the Real Dan at 11:17 PM on August 28, 2011

Seal it with a PVC cap and PVC glue. The trap is likely dry since it has not been used in ages. Sewer gas is getting in, and it is a very likely spot for a back-up to flood into the house.
posted by Gungho at 4:37 AM on August 29, 2011

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