Sewage gases: check valve?

[Aaron Fude]

Hi,

My washer is basically at the same level as the main stack (or whatever its horizontal equivalent). So there is not sufficient elevation to have a p-trap on the exhaust (take my word for it - I just can't do it).

So I bought a check valve at HD. I think it's intended for a sump pump. Will it solve my problem?

And if so - what's the best location to install it. The PVC exhaust that the washer drains into has a vertical part that then flows into a horizontal part. Is better to install the check valve is far down the stream as possible? or the other way around? or six of one?

Many thanks in advance!

Aaron

[Jim Elbrecht]

No - if it is a check valve, it will catch lint, clog & never shut properly after about a week of use.

This is what you want-

HD carries them as a "cheater vent" - Put it on the top of the pipe that your washer drains into- and sani-T the drain hose. [there should be directions showing installations in the package]

Jim

[trader4]

That solves the problem of not being able to have a vent pipe on the drain where it is located and works with a P trap. It does not eliminate the need for a P trap, which is what the stated problem is.

He says there is not sufficient elevation for a P trap, for which I think we need more explanation..

[Jim Elbrecht]

I am not a plumber-- and I know some codes don't allow them. But they work fine as a vent, and don't allow sewer gas into the house. [the latter being the purpose of the p-trap, right?]

I agree here- a picture of the setup would probably elicit a 1/2 dozen ways to attack the problem.

Jim

[trader4]

They work as a vent in COMBINATION with a p-trap. In an installation with a p-trap and conventional vent pipe, the water in the p-trap blocks the gases from coming into the house through the drain and the vent pipe gives the gases an alternate low pressure exit out the roof. The device you recommended, commonly called an air admittance valve, is used where you can't provide a nearby vent pipe, like a kitchen island sink. It allows air in, to prevent a vacuum from forming and allowing water to flow normally. It will not allow waste gases to come out through the valve in the reverse direction. But the gases will still flow right out of the drain if there is no p-trap filled with water. Also, the air admittance valve depends on there being some other actual vent pipe in the system.

Yes, since the typical washer can pump probably as high as the ceiling, it would seem a p-trap should be able to go somewhere.

[greenpjs]

Yes, but you are talking about two separate things. The p-trap keeps gas from entering the house via the drain in question. The device you are talking about lets you create a vent inside the living space without letting sewer gas enter via the vent. The OP has the first problem, not the second. He wants to keep gas from entering via a trapless drain.

[RicodJour]

I'm sure you're right. Washers are one of the easiest things to squeeze a trap in because of the capabilities of the built in pump.

R

[EXT]

If there is not enough elevation to install a "P-trap", you will find that a sump pump check valve is built to be installed vertically so that the ball closes the pipe by gravity, so there may not be enough room to install it either.

[bud--]

Interesting idea. But the description is "breaks siphoning action caused by draining water" and "keep water seal in trap" and "located at least

6" above trap arm top". It is intended to add a vent to a P trap. Without the trap there is nothing to prevent sewer gas from coming into the house.

Ditto.

[JIMMIE]

I have a friend whose main sewer line goes across one wall of his basement at about the same height as his washing machine. The washing machine connects to the stack about 3 ft above that. He eventually moved the machines upstairs when his kids moved out.

Jimmie

[Tony Hwang]

Hi Gas check valve? I wonder how it works.

[Wayne Whitney]

Sorry, you must have a p-trap and standpipe. As others have mentioned, you can raise the inlet of the standpipe as needed so the outlet of the p-trap is high enough to tie into your horitzontal drain. The pump on the washer should be capable of pumping high enough to get to the standpipe inlet. Check your washer manual for the maximum height.

If you really can't make that work, then the only alternative is an ejector pump.

Yours, Wayne

[clare]

I cannot envision an installation where a "P" trap could not be installed. - with a cheater vent - if it is possible to connect and drain without the trap.. The "P" might turn into an "S", but that's no problem.

[clare]

Big advantage of the "cheater" is it keeps the drain from siphoning the trap dry.

[Aaron Fude]

Wayne Whitney wrote: he maximum height.

Thanks for the responses. Here's my situation.

The washer is in the basement. The 4" cast iron drain runs 18" below the ceiling. So to have a 36" standpipe I would need to go through the ceiling and into a bay in the wall on the first floor, which I can't do because my wall sit on steel beams.

Thanks!

Aaron

[clare]

36" standpipe is to get above "flood level". At 18" below the ceiling you are already well up there.

You say 18" below the ceiling. Is the ceiling level the subfloor above, or below the floor joist? If it is below the joist you have another 8" +/- available. What drains are already available (what taps into the 4" CI pipe) and where? If you have a drain coming into the pipe that you can tap into I'd put a "T-Y" in and then a trap with as much "standpipe" as you have room for. If you are within a couple feet of the "stack" you may not need aditional venting if the standpipe is between something like 18" and 40" horizontally from the main drain.

Or you MAY need the "cheater vent" to keep the trap from being sucked dry.

I tried to bounce this off a friend of mine who is a retired plumber but he's not in at the moment. I'll see what he says when he gets in.

[clare]

OK, got in contact with my plumber friend. It's simple. If your washer will pump high enough to reach the pipe you put a connection into the TOP of the 4" lateral (means cut into pipe and use mechanical joint (clamped in rubber T Y)) to 2" or 1 1/2" plastic, a

45 to take it straight up, and then a fitting to clamp the washer discarge tightly to that pipe. No trap or vent required. Enough water stays in the pump of the washer to seal against sewer gas. (in most cases). If you do get sewer gas smell, simply put an S trap in the pipe. No vent required. If it is a front loader and the pump is not rated for the full height, put the washer on a 2 foot high "block"

[Wayne Whitney]

Not sure what plumbing code you are under, but I believe the IPC states:

802.4 Standpipes. Standpipes shall be individually trapped. Standpipes shall extend a minimum of 18 inches (457 mm) and a maximum of 42 inches (1066 mm) above the trap weir.

So an 18" standpipe is adequate. Is there anyway you can fit that in, with the P-trap and the transition from 2" to 4"?

Cheers, Wayne

[Wayne Whitney]

This sounds like poor advice. Wayne

[clare]

It is totally safe and legal. The plumber I talked to, a good friend of mine, was one of the best in the area for many years up to his recent retirement.