We have a foul odor coming from the shower drain in the bathroom off the first floor master bedroom. I would describe it as an extremely smelly boy's locker room smell. It occurs about a minute after we are done with our shower, building until the smell is unbearable. It usually lasts an hour or two after ending the shower. The smell has been with us about 2 months. We have tried Drano, the bleach method, snaking the drain pipe, enzymes and other do it yourself tricks offered on the internet but it has not gone away. We have had 3 different plumbers over and they cannot figure out what is going on. All three have confirmed it is NOT a sewer gas odor. One said he had never seen a trap configured like ours but didn't have any suggestions other than to try to get in touch with the plumber who originally installed it. The other 2 showers, sinks throughout the house and toilets do not have this smell.

The house is built on a slab and is 4 years old. The shower is in a large shower stall. It was a change in the original plan which called for a shower/tub. We have called the plumber who installed the plumbing but they are reluctant to come. We are worried we will have to dig up the floor as we won't be able to sell the house as is.

Any suggestions would be very much appreciated! Thanks for your help.

Is your shower base a plastic / fiberglass / composite, or a custom tiled mudset?

It has a custom tile murder.

That's mud set

I've been involved with several mudset shower bases that have an incorrectly installed shower pan liner.
Liners must be installed with pitch towards a drain assembly with weep holes that allow water / soapscum, etc that wicks through grout joints to end up in the shower drain; this prevents sour, bacterial action from occurring if the water sits in an unpitched pre - pan between the mudset & liner.....

Is digging up the floor the only way to know if this is the problem?

If your house is four years old call the builder they may help to resolve the issue, you have tried Drano, the bleach method didn't help, do one thing else it may help

Mix 1/2 cup table salt with 1/2 cup baking soda, stir and dump down the drain followed by a cup of vinegar, step back. Allow to soak overnight and flush with several large pans of boiling water. Your drain will smell just perfect, Good luck.

John

I suggest plugging the drain with a test plug, pour a gallon of water into the shower base and let it sit overnight - if the odor returns you'll know it's not coming from the drain...

Can you ask the other plumber, who commented on your "unusual" trap to describe in detail - and perhaps, to draw a sketch of it, so we can see what it looks like ?

As mentioned by John above, builder is responsible for his work for 10 years. Call him, ask him to deal with it

Question: when you look inside the drain ( with flash light ):
1. Do you see standing water inside the trap ?
2. Any white, slimy, substance on the walls of the pipe ?

Back to you

Milo