Sewer smell after shower/bath (occasionally)

[Toribean]

We recently started noticing a strong sewer smell from our downstairs bathroom when we were draining the tub after taking a bath and once or twice after a shower. The shower is used daily and does not produce the odor often. However the last 3 baths that were taken, the smell resurfaced. The home was built in 1955 and was recently fixed up after we bought it (a little TLC) and one major fix was all new plumbing.
I've read a few forum posts on similar topics and several suggest that it may be a hair/soap mixture that has gotten trapped somewhere in the pipes or a p-trap problem. I'm leaning, and hoping, more towards the hair clump (although we don't seem to have any standing water) but I am not sure what the most idea and safe thing to put down the drain is. Bleach, vinegar, olive oil, chlorine....? If any of these, what's the proper dosage?

Any help or suggestions are greatly appreciated.

[LiQuId]

its likely a venting issue if as you say the plumbing is new.

[Caduceus]

I would look into the possibility of hair, soap scum, etc. in the drain. It may be before the trap and the odor is coming from the overflow part of the tub. If there is a slight clog further downstream, the trap seal could also be compromised and allow sewer gas to come through after a large volume of water is let go, such as after a bath.
If a remodel was done and new piping was connected to the old, hair can build up at the connection of the two if there is not a flush connection of the piping.
Also, as Liquid stated, if the tub wasn't vented during the remodel you could be losing the trap seal. Any way to show a picture of the piping and trap?

[Toribean]

Thank you for the quick responses. I think I'm going to try a little bleach (unless otherwise suggested) this morning and see what happens. It's odd how we don't smell it everyday though, mainly after a bath that is when it's the most obvious. Getting a picture though unfortunately isn't an option because the way the ducts are set up under the house makes it difficult to get under there, unless your smaller in frame which thankfully our plumber was.

[desertwater]

I would run the shower just long enough to fill the trap. Then fill the tub and drain it. then with a flash light look down the shower drain, if theres no water in it then you maybe have a venting issue and the tub is siphoning the trap of the shower.

[Toribean]

No luck with the bleach yesterday, it seemed to aggravate the smell. It seems to be more potent around the base of the toilet which is right next to the shower/tub. We have a full bath upstairs as well & we are going to try a shower tonight & see if the smell surfaces. Either way we're thinking we'll have to call the plumbers that put it all together for us 6 months ago, hopefully theyll have a quick fix.

[DUNBAR PLUMBING]

Leaking wax ring.... it's allowing sewer gases to escape. Happens constantly and the new products used for the wax on these rings are starting to show signs of shrinking over time, thus causing issues.


It's a terrible scenario to know this design is showing up with this type of product.