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Sewer odor from shower drain

My home is 10 years old, single story, slab on grade. For the last month I have been getting a sewer odor whenever I take a shower in my stall shower. I have put some "Liquid Plumber" in the shower drain, checked that the drain runs freely, but the odor persists. The stall shower is equipped with a fiberglass pan, so there doesn't appear to be any leaking around the drain fitting.
As a temporary measure I cover the drain when not in use with a flat rubber stopper. The other drains in the bathroom(tub, double sinks) do not appear to exhibit the problem. Any suggestions?

Re: Sewer odor from shower drain

Sewer odors usually points towards a venting problem. Meaning that the drain line isn't vented correctly (not uncommon in slap-it-up new construction)... and therefore the vacuuum created by the water running down the drain causes the water to get sucked out of the trap.

Could also be that somehow the vent is plugged.

Had you done any work on the house or rennovations? Just trying to understand why it's suddenly become a problem now. Usually that means something has changed.

You could try pouring just a cup or so of water down the drain slowly after you take a shower. IF the trap is full, there should be no way sewer gases can come back inside.

Also possible that the trap is getting sucked clear by another drain on the same line. This is most often a toilet which has a large mass of water draining at once. Either way, that's still a venting problem.

Maybe someone else has another theory.

Re: Sewer odor from shower drain

Are you getting the odor when taking a shower or after using it? It may be coming from a fixture other then the shower. The most common is the wax seal on the toilet. Even though it doesn't leak water it can allow sewer gas it enter the room. Is there any movement between the bowl and the floor? If so that is a sign that the wax seal needs replacement.


Re: Sewer odor from shower drain

Thanks for your help....
Of course there was no odor this morning when taking a shower, but I did make some checks along the lines of your suggestions.
I'm able to look down the shower drain using a flashlight to confirm that water is standing in the trap.
I watched the shower drain water level while flushing the toilet and draining the tub. No apparant disturbance to water standing in the shower drain trap.
The water level in the drain was unchanged before and after my shower.
I poured water down the drain while watching closely for any siphoning action that would empty the trap...nothing.
The toilet is firmly attached to the floor with no rocking.
There has been no recent work done, so nothing has changed as far as the venting. I opened a cleanout plug protruding from the outside of the house which appears located to specifically serve the shower, with vent stack through the roof directly above. No blockage I could detect with a stiff wire. I don't have a snake to run in the vent line nor a ladder to climb up and drop one through the roof vent.
I guess the issue is intermittant so I'll keep watching in the same way in the future. I'll post if it happens another time.
Again, thanks for you help and suggestions.

Re: Sewer odor from shower drain

Clean the hair out of the drain with a small snake ( its going to stink and be a lot of it) then dump about 1/4 cup of baking soda then a cup of vinegar down drain let sit over night and should take care of problem.

Re: Sewer odor from shower drain

Check your drain's vent. The sewage odor may come from a blockage or lack of ventilation.

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