Sewer smell. Wife freaking out. Need help!

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Mawst95

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Hello experts. I need your help. The basement laundry room in our 1939 home is intermittently letting out significant sewer gas. Enough to smell on the main floor. My hypochondriac wife is not amused and is currently researching hydrogen sulfide poisoning. Not good.

Smell is intermittent but seems to be associated with using the washing machine. It doesn't happen everytime and the intensity varies. When I open the window above the machine air blows in fairly strongly suggesting negative pressure. Dryer, kitchen hood vent, and radon all exhaust right there to the exterior of the laundry room.

Next room over (mechanical room) has the gas furnace and gas water heater. Doors have slats. Doors to the finished basement space has slats. Basement door leading upstairs has a large gap under the threshold. There's a bathroom on the other side of the basement. I periodically flush the toilet and run water in the sink. Its vented separately. Sump pit is in mech room.

Plumber has been out twice and installed an AAV on the laundry tub as he said they were sharing a vent and could siphon(?). Hasn't helped.

We aren't experiencing slow drains or gurgling sounds.

I'm posting pics and a diagram. The way the main vent ties in doesn't look like the pics I see. If I understand correctly it looks like the laundry standpipe is wet vented. And AAVs like on the laundry tub aren't well regarded by my research.

Finally there is a floor drain but it doesn't look like an normal drain that goes to the sewer. It seems like just dirt down there. Smells like wet dirt but I get no sewer smell from it.

If you need measurements I can provide them.

Thank you.
 

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LLigetfa

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You need to follow your nose to the source of the smell. It could be a bacteria culture in a drain before or in a trap that needs to be mechanically cleaned out and not actually coming from the sewer downstream.
 

GReynolds929

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The washing machine drain is an S trap, this will cause the water to siphon out, especially with high flow washer discharge. Needs to have a vent before it turns down past horizontal.
What is the Santee on the utility sink tailpiece for? Is that the AAV? If so the plumber is a dumbass, the AAV needs to be after the trap to function as a vent.
Also make sure the washing machine drain hose is not inserted more than 12" into the standpipe.
 

Jeff H Young

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As stated above Totally agree , I dont know if he mentioned the laundry stand pipe totaly plumbed wrong as well. All of these wrong way plumbing methods can cause stink , but also possible to horrible work and not have problems some times it goes unnoticed . floor drains often are the cause. There wasent a plumber involved in this Drainage work . Id say replumb it but I dont know if ittl fix the stink but the work stinks sorry to inform you and not trying to rub it in
 

Mawst95

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As stated above Totally agree , I dont know if he mentioned the laundry stand pipe totaly plumbed wrong as well. All of these wrong way plumbing methods can cause stink , but also possible to horrible work and not have problems some times it goes unnoticed . floor drains often are the cause. There wasent a plumber involved in this Drainage work . Id say replumb it but I dont know if ittl fix the stink but the work stinks sorry to inform you and not trying to rub it in
Jeff and GR

I really appreciate it. Be candid. I didn't do the work lol. Even if I did, I wouldn't be offended as how else would I learn? The whole washing machine and sink setup (minus the AAV--and yes, that's the santee? on the sink) was before our time owning the home.

I figure having this whole setup repiped will cost a couple thousand so I am trying to educate myself to prevent additional "dumbass" work I believe is the technical term:)

I saw this diagram posted here and other forums. Is this setup something I should show a plumber as an option or just let them figure out what's best (though you saw how that worked out for me with the AAV).
 

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Jeff H Young

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Mawst95, no real need bashing the guy that did the work coulda been homeowner I hope not someone calling themselves a plumber.
I dont think Id use the drawing A lot of us are Plumbers on here and can guide you through this its not that hard mostly cutting and gluing fittings together but might be outside your comfort zone. I havent drawn these up before You would need An AAV probebly in liew of a real vent out the roof. Im still concerned with where smell is from despite the fact you have wrong plumbing going on.
Are you brand new in the house ? always had the stink ?
 

Mawst95

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Mawst95, no real need bashing the guy that did the work coulda been homeowner I hope not someone calling themselves a plumber.
I dont think Id use the drawing A lot of us are Plumbers on here and can guide you through this its not that hard mostly cutting and gluing fittings together but might be outside your comfort zone. I havent drawn these up before You would need An AAV probebly in liew of a real vent out the roof. Im still concerned with where smell is from despite the fact you have wrong plumbing going on.
Are you brand new in the house ? always had the stink ?
The person who added the AAV (apparently in the wrong place) was a plumber from a well respected plumbing company in my area (Maryland).

I don't intend to attempt to fix this myself, but I'm trying to learn enough to ask the right questions of the plumber and assess whether their proposed "fix" makes sense.

The smell seems concentrated behind the dryer where the main sewer line meets the drain line and vent heading to the roof. The issue there is that's where our Radon enters the slab. Apparently its a bit leaky due to the french drain and stippling? mesh? at the base of the walls and slab. I am concerned that the smell is being drawn to that area rather than initiating from that area. That said, I'll make an effort to try to pinpoint it.

We've been in the house for about 3 years. I don't recall noticing it until about 1.5/2 years ago. Around the same time we insulated and air-sealed the attic and did a bit of sealing around the basement rim joists. There was a blower test done around this time (to qualify for certain credits) and we dropped our air penetration quite a bit, but it's still an 80 year old house with original single pane windows that leak like a sieve. But perhaps it exacerbated an existing issue?

I did put a portable dehumidifier in the laundry room about 2 years ago. It doesn't run much if at all during the winter months.

EDIT: To be clear, the vent shown on the far right of my diagram does go up three floors and out the roof (presumably).
 

WorthFlorida

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Take a wet rag and stuff it around washer discharge pipe or plastic sheeting as Reach4 suggest. Give it a few days to see it the oder continues. It’s only to find the source, not a fix.
 

Jeff H Young

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might have actually added the AAV to make the sinks drain faster I dont know it actually hurts nothing but also does nothing toward making this a legal rough in on the sink or for the laundry standpipe. But Reach 4 and worth florida have a few ideas to locate the stink
 

John Gayewski

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RE plumb yes. Both the laundry sink and laundry standpipe are wrong. But also how far is that hose down into the stand pipe? The end of the hose needs to be well above the water line in the trap. If the hose is down in the trap it will definitely make some stink.
 

Mawst95

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RE plumb yes. Both the laundry sink and laundry standpipe are wrong. But also how far is that hose down into the stand pipe? The end of the hose needs to be well above the water line in the trap. If the hose is down in the trap it will definitely make some stink.
Hi John,

Yes I had read about that issue either here or on another forum. It's down about 6-7 inches.
 

Mawst95

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The plot thickens. I'm trying to identify the source(s) of the stink as you all suggested. Even though the piping is wrong, as you said, it doesn't mean that's where the stink is coming from.

So I plugged up the standpipe AND the laundry tub with a wet rag while we ran the washer and the dryer. My wife did a few loads. Afterwards, I unplugged the sink--no obvious smell (though it's hard to get my nose really right into the drain). I then unplugged the standpipe--no smell. I got my nose really into the standpipe--nothing. Smelled like slightly musty laundry detergent. I smelled the floor drain--nothing.

With everything unplugged I then decided to start another laundry cycle. About 2 minutes into the cycle (water had just started running), I decided to stop it as it was time to put our son to bed and we figured we'd do more trouble shooting this morning.

About 2 minutes after stopping the cycle I started smelling it. Faint at first and then stronger. I quickly smelled the laundry drain and the standpipe but they didn't smell to me. It smelled around them, but unless it was a single burb of gas that I missed, I really didn't think it was coming from there. I also heard some water from the floor above drain down the pipe connected to the vent stack--perhaps from the kitchen sink. My wife also said she flushed one of the upstairs toilets around this time, but that toilet uses a different waste pipe I think.

By my nose it smelled a bit more by the dryer, where the vent stack is on the far right of my pictures/diagram. Up in the corner where the vent pipe (looks like original cast iron?) runs along the rim joist before I assume turning upward I saw spider webs fluttering. There was clearly a draft coming from back in there. I got up on the dryer and smelled the draft blowing in and it stunk. Now I did see a dead mouse up there, which may have exacerbated the smell, but I doubt the mouse is the sole source of the smell. I've smelled dead animal--it's a bit different than sewer. It also would smell all the time, not just when we do laundry.

Right now there are too many variables--some may have mattered and some might not. Plugging up the sink and standpipe may have messed with the air flow, so I'm going to wrap the entire sink in a plastic drop cloth, but keep the drain unplugged. I'll then do the same with the standpipe. That should let me eliminate those as sources--though the way they are piped could be a contributor.

Not sure if the water draining from the floors above are relevant or not. Will try to recreate the situation tonight. Will also smell that corner with the dead mouse when nothing is running to be sure that it doesn't smell. My only thought there is running the laundry could create negative pressure which is pulling air in that passes over dead animal. That seems like a long shot.
 

Mawst95

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No, but I think you are right.

We had another plumber come out. She pointed out that 1) the AAV was in the wrong spot, and 2) the entire plumbing of the washer and sink was suboptimal. She fixed the AAV, capped off the stand pipe and said we should drain the washer into the sink for the time being to see if that solves the issue. She offered to refund our money if it didn't work (an offer I have no intention on taking her up on. She did the work regardless of whether it fixed the problem.)

The company of the previous plumber who put the AAV in wrong refunded me and gave a sincere apology.

Spoiler: The smell is still there unfortunately. The second plumber does not like the way things are vented. She thinks that when they put on an addition to the house they screwed up the venting. She wanted to try to fix the AAV issue before doing something more drastic.

I have been meaning to use the plastic idea suggested above. I have just been bummed about the whole thing and busy at work so haven't had the chance.
 

WorthFlorida

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I asked because I'm following another post with similar issues but it spreads into the living area. A smoke test is about the best way to find the source of the leak. At least you found a good plumber.
 

Jeff H Young

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Cant remember all the details and didnt read through a bunch of posts but looking at a few pics and drawings running the wash machine into the sink along with reworking the aav. and capping off stand pipe . makes a a world of differance an honest attempt at getting things right. And I agree that shouldnt guarantee there arent other issues . I hate to see you crack the floor just yet , Id give the smoke test as a thought without really reviewing the entire situation it might be a good idea. We here are all supporters of plumbers , trades people and those with a want to DIY . so come on back with more questions
 
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