How can I tell if my shower has a p-trap?

[CenTex]

We're on an aerobic septic system and seem to have a lot of sewer gas coming up the shower drain. After reading some posts on this forum, I'm wondering if the builder failed to install a p-trap for the shower stall. Or if it was installed improperly (at a severe angle, etc).

Is there an easy way to tell if I have a p-trap at all? House is on a slab.

 

[Smooky]

Shine a light down the drain and see if you can see water standing in the pipe. If you just see pipe and no water, then there may not be a trap.

 

[Sponsor]

 

[Jadnashua]

A common problem with many showers is the installation of a liner, flat on the floor and/or blocked weep holes to the drain. If that exists, the pan cannot drain fully, water can build up underneath the tile, and that, by itself, can start to smell like a swamp. It often takes a few years.

A second problem could be that on the slab, they decided that no liner was required at all, and either the curb and/or floor plates are all rotting.

If you see water in the trap, it's not that.

 

[CenTex]

Thanks for the input. Yesterday I did a little more testing and believe septic gas/venting is not the issue since there is water standing in the shower drain. I took a rag and sopped out a good bit (smelly and grungy) and the level remained down about 3 inches. This made me think there is a trap installed, per Smooky's reply. However, I found that when I run water from the nearby sink or tub (but not the toilet), I could see movement in the standing water in the drain. Plus a little "gunk" washing into view. The level of the water (in the shower drain) also rose and remained up.

Now I wonder if there might be a faulty drain line angle (sorry - I don't know the correct terminology) at this (the far) end of the house? I don't understand how flow from a sink could enter into the shower p-trap if installed properly. Could gray water be "standing" in the line? Is it possible?

1999 ranch, built on slab, PVC lines, problem at far end (about 60' from septic tank)

 

[Reach4]

I am not a plumber. I would stick a medium Brasscraft drain bladder down the shower drain and turn on the hose. I would watch the sink for water rising there. There may be a partial obstruction in the drain pipe after the sink drain. Maybe the pressurized flow will move something along. Do you have a cleanout nearby?

 

[Jadnashua]

If the shower is not vented properly, drainage from other devices upstream of it can cause the p-trap level to change. In the worst case, it could siphon it enough to let sewer gasses enter. If you can see water flowing beneath the shower in the pipe from the sink, you may have two problems: no trap and a blockage. Normally, standing water is the result of a p-trap, but a clogged pipe might look similar.

An improperly built shower can really smell raunchy and have nothing to do with the drain system.

Improper grade or pitch to the drain system could lead to standing water and/or blockage, but more typically, you'd notice slow drains verses smells.

 

[CenTex]

Thanks again for the input and ideas. No slow drain problems - sinks or shower. Blockage idea must be explored, it seems. No clean out nearby. I do have a small drain auger I could try passing into shower drain.

Our shower stall is in a corner of the room, made of individual boards/panels of what I have always called "cultured marble" (fiberglass?). When we first bought the house (14+ years ago), there was a problem with water collecting under the shower floor, probably from a failing caulk seal around the perimeter of the floor. The floor panel was set onto what looked to be mortar mix or just sand. Man - did that water stink! I hired some guys to fix it and they did a great job - pouring resin in under the floor panel. It's solid now and caulk is still secure. I'm pretty certain the smell is not from standing water under the shower floor panel.

After sopping the standing water in the drain, the smell disappeared. Then I ran the sink, the shower drain level rose a few inches, and smell returned - almost like the sink draining was pushing stuff into the shower trap (if it is one). So I cleaned the sink trap (smelly but not clogged), then flushed clean water for a minute or so. Saw slight turbulence in standing water in the shower drain, but no smell. And this morning, there was no smell from the shower drain, which is not the usual case.

Could the problem have been as simple as needing to clean out the sink trap?

 

[hj]

The trap does NOT prevent water from backflowing into the shower if the drain line is obstructed, which is what your description indicates.

 

[CenTex]

Update: fished a drain auger down the shower drain - nothing. But did the sink and at about 12 feet, it seemed to hit something. Gave it a twirl and continued another few feet. Upon withdrawal, no evidence of a clog on the auger. Ran a lot of water down sink drain and continued to see floaties in the shower trap. But they were getting fewer. And the smell was gone. Continued with more water down sink and it might be okay now. I guess it might have been a partial obstruction in the drain branch? And was diverting gray/grungy water into the shower trap? Just glad the smell is gone. I'll repost in a couple of days with an update.

 

[CenTex]

Final post: Have used shower twice with no smell. Also sediment in bottom of shower drain trap is gone. Success! My thanks to those who offered suggestions.