The Mystery of the Smelly Shower Drain [long, but would love help]

1,402 Views | 11 Replies | Last: 1 mo ago by billyjack2009
bagger05
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Sorry it's long -- want to give all the background. Any help would be GREATLY appreciated. This is frustrating the crap out of us.

Summary: sewer smell coming from the shower drain after we use it, goes away after an hour or two; inspection of the plumbing and the vent by plumbers show no issue; the smell remains.


2020 we bought a 100 year old house. Renovated everything, including all new plumbing. PVC everything.

For three and a half years everything was fine.

A couple months ago we noticed a bad smell when we'd take a shower. Smelled to us like sewer gas. That plus some slow draining made us think it was a clog.

We had a plumber come out and get it cleaned out. They removed a ton of gunk and put in some kind of "enzyme treatment." Started draining fine and the smell went away. But only for a little bit.

Within a week the smell was coming back.

We tried some home remedies. Baking soda and vinegar. Bleach. Didn't help.

So we called the same plumbers back out to investigate further.

They went under the house and inspected the plumbing. They said all is well underneath. They said the next step was to inspect the vent, but they didn't have the equipment for it. We made another appointment for them to come back out.

After this visit we stopped using the shower in question. Had some scheduling trouble so it was over a week before they could come back.

They showed up and ran the water for a solid five to ten minutes. Of course now there's no smell. But they went ahead and inspected the vent anyway. They went into the attic, cut into the vent, and ran the camera down. They said there's no problems they could see with the camera.

At this point they said they were at the end of what they could do. They said the next thing would be to get a smoke test (but they don't do that).

I went back to using the shower since the smell was gone (and I was hoping the problem had magically healed itself).

First shower (a few hours after the plumbers ran the water): no problem.
Second shower (the next morning): the smell was back.

I got down on my hands and knees and put my nose to the drain.

1000% this is where the smell is coming from.


I emailed the original plumbers and told them my observations. Was very nice and made it clear I wasn't mad; just confused by the situation. I asked if they had any further advice. They said that it could be a bad tile job that caused water to get between the tile and the pan of the shower.


So here's where I am:

1. The smoke test doesn't make sense to me since it is clear that the smell is coming from the drain (when the guy recommended that, we couldn't reproduce the smell so not throwing stones on that). My understanding of a smoke test is that it's good for finding the source of a smell when you don't know where it's coming from. Not the case here.

2. The thing about the tile doesn't make sense to me either. Seems that if that was the issue it would smell like mildew, not sewer. That said, visually it looks like the tile isn't sealed properly. Grout is crumbling in spots. And the tile subcontractor sucked, so if he screwed it up it wouldn't surprise me.


Feels like this should be relatively straightforward. We know where the smell is coming from and when it happens... not sure if the plumbers could've missed something or what.
sts7049
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is the P-trap in the drain holding water like it should?
Pinochet
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Has anyone looked at it with an infrared camera to see if there is a leak in the pan that is causing/allowing sewer gas to come back past or around the P trap? Just spitballing, but maybe the pan and the drain are compromised somehow, but the water eventually finds its way back to the trap to block the gas?

Is there any other fixture sharing the same vent?
bagger05
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sts7049 said:

is the P-trap in the drain holding water like it should?
Of course this is coming from a person who doesn't know much about plumbing but I think so.

1. They inspected under the house and I think if it was installed so that it wasn't holding water or if it was leaking then they would have seen that.

2. Also the smell only happens while we use the shower and right after. Again, I don't know much about plumbing but if it wasn't holding water wouldn't it smell bad all the time?
bagger05
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Pinochet said:

Has anyone looked at it with an infrared camera to see if there is a leak in the pan that is causing/allowing sewer gas to come back past or around the P trap? Just spitballing, but maybe the pan and the drain are compromised somehow, but the water eventually finds its way back to the trap to block the gas?
I don't think they looked at anything with an infrared camera in the bathroom or under the house. They used a camera when they inspected the vent but I don't know what kind.

I think you're saying the same thing these guys did about maybe there is water getting between the tile and the pan? I think that is very possible. Like I said the tile subcontractors were probably our worst ones and it looks like they didn't do a very good job. In the corners of the shower the grout is kinda crumbling. In other parts of the shower it's like the grout is getting washed away. Like it wasn't sealed properly (I don't know anything about tile, either, so I don't even know if that's a thing).

I'm trying to understand how it could cause a sewer smell and the plumber couldn't really explain it either. But they said they'd seen it be a problem before, and at this point we'd be willing to try anything. We need some tile work done in there anyway.

Quote:

Is there any other fixture sharing the same vent?
Yes, the toilet vent joins up with this one in the attic. The sinks are on a different vent.
Beckdiesel03
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We had a bad tile job that was causing water to get stuck between the tile and the pan/liner. Tile guys came in and demo'd the badly formed pan, poured a better sloping one and redid the base of the tile. No more smell for us, and yes it was a sewer smell, not a mildew smell.
coppellag82
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Pretty sure I know what your problem is. We had the exact same thing years ago. Biological material (dead skin, ect) is trapped between your shower floor tile and the pan base under the tile. When it gets wet it stinks. Here is how to fix it.

First cover your drain and then get some Simply Green or similar and pour onto your shower floor. You need to cover the entire floor to at least 1/2 inch deep. It will seep under the tile through cracks (probably where the floor tile meets the wall tile and the caulk is cracked). Let it sit for several hours. Next drain and let dry completely. I'd put a fan in there and let dry for a day. Next, and this is important so your problem doesn't come back; inspect and re caulk the joints where the floor meet the walls. The back corners where the shower spray hits is generally the worst spot. Also look for any cracks in grout on the floor. Make sure you use the correct shower caulk. Go to a tile store and ask them.

After caulking, let everything dry.

This should solve your problem. Takes a couple of days but it fixed mine.
bagger05
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Beckdiesel03 said:

We had a bad tile job that was causing water to get stuck between the tile and the pan/liner. Tile guys came in and demo'd the badly formed pan, poured a better sloping one and redid the base of the tile. No more smell for us, and yes it was a sewer smell, not a mildew smell.

Thanks that is encouraging. Do you happen to be in Dallas?
Beckdiesel03
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We are not, otherwise I would give you the tile guys contact info. It was a relatively cheap fix all things considering. Just had to go to home depot and fine a new tile that would match the existing wall tile. Originally I was worried we were going to have to redo the entire shower.
jt2hunt
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coppellag82 said:

Pretty sure I know what your problem is. We had the exact same thing years ago. Biological material (dead skin, ect) is trapped between your shower floor tile and the pan base under the tile. When it gets wet it stinks. Here is how to fix it.

First cover your drain and then get some Simply Green or similar and pour onto your shower floor. You need to cover the entire floor to at least 1/2 inch deep. It will seep under the tile through cracks (probably where the floor tile meets the wall tile and the caulk is cracked). Let it sit for several hours. Next drain and let dry completely. I'd put a fan in there and let dry for a day. Next, and this is important so your problem doesn't come back; inspect and re caulk the joints where the floor meet the walls. The back corners where the shower spray hits is generally the worst spot. Also look for any cracks in grout on the floor. Make sure you use the correct shower caulk. Go to a tile store and ask them.

After caulking, let everything dry.

This should solve your problem. Takes a couple of days but it fixed mine.


Taking a shower allows water to push the smelly junk out and into
The drain !
gabehcoud
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Most likely is cracked p trap. Get a flashlight and rule that in/out first. If you don't see water you've found the problem

billyjack2009
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We had a similar problem. 1988 house. Had the foundation leveled twice (Houston) and started noticing a smell in the master shower. Had the sewage pipe running to the main line replaced due to tree roots thinking that would solve all of our problems but that only solved the drainage problem. Eventually figured out that the house shifted so much that the drain pipe wasn't centered under the pan drain hole and water/misc was seeping between the pan and the slab (or something like that).
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