Smell in Laundry Room

Need insight on what may be causing a smell in our laundry room that smells like sewer gasses. We moved into the house in August, and had no issues until the end of December with this smell. In the beginining of November, I replaced the previous owners gas dryer and old washing machine with our HE Samsung units from our last house. The smell is not coming from the washing machine, and I have cleaned its filter and the seal on it regularly. The room does not have a floor drain. Also the line from the washing machine is only a couple inches down the pipe, and isn't past the p trap.

The laundry room is on the first floor of our house, with access below to plumbing. The line for the washer is the first one off the main drain line. After exhausting my level of diagnosis and putting up with this on again off again smell for ~3 months. I had a plumber out who replaced the p-trap as they thought maybe it wasnt installed level or had a crack that was allowing gas to pass through. Well this morning the smell is still there.

Is it possible this is a venting issue? None of the drains have any issues draining and there is no gurgling of water indicating a vent issue. Just at a loss as to what is causing this smell. Sometimes its mild or non-existent, other times it's pretty awful.

Any insight is greatly appreciated.

Is there by chance a floor drain with no side plug or the trap is dry?

There isn't a floor drain in the room, and we primed the trap after installing. Plus we run laundry about every day. I just cut a hole above the washing machine stand pipe following the vent line. I was thinking maybe the previous owners had pierced it when they put in cabinets that I removed. No such luck, and now another section of drywall to patch.

The discharge on your newer style washer maybe blowing the trap seal out. How is the stand pipe for the washer discharge piped up.

Here is a picture of it. Before I had the plumbers out. I did drop a nut on a string down and it was wet. The plumbers did mention this is 1 1/2” vs code is now 2”.

Are you sure he was a plumber. He should of cut the 2”x1 1/2” santee out and put in a 2” santee instead of using a reducing no hub connector. Also it looks like he used a union trap that will be concealed behind drywall.

The T was already there, and they replaced from the silver connector over. They used the union joint stating if issues this will easy in assess. He was also referring to putting a access panel back on rather than drywall since this is behind a fridge. However I will likely just replace with drywall, if I ever figure this smell out.

Assuming this is the only trap in this room. No sink?
I would try to confirm that smell is, in fact, coming from the standpipe.
A wet nut on a string does not confirm a water seal.
Try adding a cup or 2 of water, into the standpipe, after each washing machine empty cycle for awhile and see if smell persists or subsides.

What else is that vent pipe serving below?
Is it acting as a drain for something above?

CT18 said:

The discharge on your newer style washer maybe blowing the trap seal out. How is the stand pipe for the washer discharge piped up.

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My feelings on that happening, even with those high flow washing machines, is that it's more likely to PULL a standing trap seal, from the discharge side. Not push it out. Doesn't the machines discharge volume tamper off near end of spin dry cycle?

is your washer a top loader or a front loader?

the newer front loaders have a problem with not draining all the water
then the water stanks.

if i were you, i would stuff a rag around the drain hose where it enters the stand pipe
then, see if the smell stops, this will let you know where the funk is coming from


the 1 1/2 drain concerns me. that could very well be the source of the problem...to small
causing siphon

Above the laundry room is my daughters bed room. The wall that the vent pipe is in doesn't have any plumbing fixtures adjacent to it. My daughters room does have a full bath, but I assume they ran the drain line for that before entering the basement, or one of the other large lines must t off somewhere in the walls.

The washer is a newer front load washer, however we used it at our last house for 6 years without issue. I will try and see if adding water after each load makes a difference. Want to say we tried that before though. Willing to try anything that makes sense at this point.

Albert Dowling said:

The washer is a newer front load washer, however we used it at our last house for 6 years without issue. I will try and see if adding water after each load makes a difference. Want to say we tried that before though. Willing to try anything that makes sense at this point.

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Or as @frodo suggested, use a rag if you feel you can get an acceptable seal.
The main thing at this point is, to try to confirm the source of the smell.
So there is nothing else connected to that drain pipe below that level?

You had mentioned, "Is it possible this is a venting issue? None of the drains have any issues draining and there is no gurgling of water indicating a vent issue."
At this point, we can't rule out that it isn't a venting issue causing a lack of trap seal. With or without other draining issues and no gurgling. Would all depend on if, where or how the vents were connected.

I have placed duct tape several layers around the washing machine hose, making it a snug fit. I will add water after running loads of laundry and see if the smell persist. I am pretty sure I did this when we first noticed the smell. But doesn't hurt to try again.

The drain pipe (part in the t of the picture) runs down to a 90 degree elbow right beneath the floor and then over to the main. Above the t, I don't know if that is connected to anything else, or just to the attic and then out the vent.

Well think I solved the issue and wasn’t plumbing at all. Now to repair the drywall

LOL...Had your smells mixed up.
Glad you found it.
Set out those traps.

Albert Dowling said:

Well think I solved the issue and wasn’t plumbing at all. Now to repair the drywall

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Doh! That'll do it!