The problem: a sewer gas small that fills our 2nd story master bathroom

When: It most often comes in the evening after 9:00 PM although occasionally it does come in the daytime after we have run water.

Where: We cannot locate with our nose the specific source of the smell in the bathroom

What has been done so far to address the issue with plumbers:

• We poured hydrogen peroxide and other in the shower drain multiple times

• We snaked the shower drain.

• We plugged the toilet drain

• We plugged the shower drain

• We plugged the sinks

• We replaced sink piping

• We replaced the pluming under the house.

• A smoke test was done through the whole to determine if there is a break or leak in any pipe and the system
was solid.

• We replaced the septic field

• We pumped the septic tank

• We put chemicals down the drain to create healthy bacteria in the septic tank.


Other notes:
This bathroom sits on top of another bathroom below
The smell comes with the window open or closed

The plumbers in are baffled. I welcome any ideas from experts.

You may have to have someone get on the roof and use peppermint oil. I am just throwing some ideas out here, a smoke test is usually the answer, but if it was already done and done correctly.. Just a thought, but does your air conditioning usually stop running in the evening around 9? Have you tried checking other sources for the smell, like ductwork or in the attic? If the AC stops running, then the air probably stops moving and that will let smells accumulate. It could also be that your roof vent is partially plugged and higher volume usage in the evenings is sucking a trap dry somewhere, but it gets refilled with later use, and thus wasn't found during the smoke test.

Thanks so much for this reply I will follow up with your suggestions. We do not have air conditioning and there is no attic space above the bathroom for others to consider.



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This is an extreme example, but have you considered a powered vent on piping that exits your roof? Could barometric pressures be an issue in your area ?

Best Wishes

Can you see the stack coming out of the roof? I have heard stories of contractors not pentrating the roof because they figured the roofer was going to do it. Just thinin'

I would guess that venting was not executed correctly possible in the upstairs bathroom

I'd start with making sure the vent from your bathroom fixtures is actually tied into the main building vent. Once this is confirmed next move on to assuring that the terminal vent is run through the roof, its possible that the plumber was a hack or just stubbed it into the attic and forgot. You said you did the smoke test? My issue with that is that much of the piping is inside walls and it would be possible for a cracked pipe inside a tightly sealed wall to go unnoticed. After all, today's building codes are made to prevent fire and smoke from moving up through walls like the old balloon frame buildings. The only way to truly know your plumbing is tight is to isolate fixtures, your vent riser, and your sanitary lines running out of the building using test balls, jim caps, and an air compressor. This is most likely beyond your average homeowner skills but an experienced plumber could figure it out. You've clearly eliminated all the obvious and accessible problems so my guess is an open fitting or cracked pipe inside the wall or a bad venting job. I can't see it being barometric pressure because the p-traps would block a downdraft in the vent. Hope this helps.

Do you have an air admittance valve under the bathroom sink?

How many walls do you have waste pipe in? Can you drill a 1/4" hole near the pipe in the wall and insert a 1/4" neopreme or plastic hose inside and smell through the tubing? it may tell you where you need to remove drywall. I would exhaust all other suggestions first just to make sure the vent is installed properly ( installation and sizing).

I don't think barometric pressure is an issue here. But I'll propose your idea to our plumber....thank you.

We can see a stack coming out of the roof

These responses are so very helpful. Some of the answers to your questions I will have to have my plumber help answer and I will get back with more information.



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