Shower Stench Problem

Hi, great forums. From searching I've learned a lot about my problem I think. Here it is:

A few times a week we have a horrible stench that comes out of our shower drain.

We are on city sewer.
This is an upstairs shower.
We have seperate tub and shower in this bathroom.

At first I thought that we had a blocked vent pipe. One time my wife raised the toilet seat and found a DEAD SQUIRREL floating in the water - so I thought that maybe another had gotten wedged in a pipe and died.

Now after reading up a little bit and a little investigating on my own I believe that we have some sort of P-Trap problem.

The shower is used everyday so there should always be some water in there to block the gasses, but somehow I think the water level goes down enough so that they can seep in. { I just took a plunger and forced the water down further and the stench really started pouring out - so I think I'm on the right track with this.}

The piping is in my floor so I can't tell if there is a proper P-Trap installed.

What is there to do? Rip out the ceiling below and examine/fix the pipes? Or am I totally off-base and it could be something else.

Thanks for any help,
Stinky

I don't have a real answer for you, but I agree with you think that you are on the right track. I wonder if since the trap is under the floor, perhaps because of lack of space the trap was installed improperly and so it never totally keeps the water. I fear that you may have to open the floor to inspect/repair the problem, but perhaps some of the real pros will have some ideas about other possible causes. I think I'd put a wire mesh over the vent intakes to keep critters out.

If the vents aren't done properly, running water down one drain can pull the water out of a nearby trap...do you hear anything or see anything like the water moving in the toilet when running water in the sink or the shower or gurgling in the sink trap?

No, we don't see any movement of water or hear gurgling from any other the other drains.

I've been keeping an eye on the water in the P-Trap in the shower (removed the drain cover) over the last 24 hrs. It hasn't gone down any, but there is still a smell coming out of it. Is it possible for gases to pass through the p-trap water?

There is another, totally unrelated to drain possibility that could cause your shower to smell...it doesn't have a preslope under the liner. A properly built shower is made up of multiple layers - a loose concrete/sand mix with a slope to the drain, a waterproof membrane attached to a clamping drain, more sand/concrete/mortar mix on top of that, then thinset and tile. If the builder placed the waterproofing on the flat floor, any water that gets through the grout (not much, but it builds up), it falls down to the bottom of the pan and sits there since there is no slope to the drain. You end up with a swamp under the tile. The vast majority of water flows down the tile to the drain, but each shower, a little soaks through the grout, even if it iw well sealed. If the thing is built properly, any water that does get under the tile through the grout or cracks, etc., get to the liner, which is sloped to the drain, and it escapes through weep holes (that must be kept open during construction) to the drain...no standing water under the tile, and because of the sloped liner, it dries out.