Sewage Smell in the bathroom

Here is a question for all the plumbers out there. This is not for a house that I inspected; I actually built this house for a client last year. A strong foul smell of sewage is coming out of the shower drain. This is a shower pan with a concrete and tile floor. We have already cut out the ceiling below to make sure the plumbers didnt forget the P trap. We went in the attic to make sure it was vented. Both were fine. Now the clients are pist and want it fixed. We called the plumber back and he does not know what is going on. Does anyone have any advice on what I should do? Because I dont know what to do at this point. DIABOLICAL :twisted:

Tyler Tachell
To the T Home Inspections

If all of the components are there but they are not operating as intended, I would say there is another condition in the building that prevents its proper operation.

Building analysis that I frequently perform takes into account the entire building when evaluating a situation, not just the plumbing system (or whatever system is failing).

What would cause the smell to enter the house?

#1 there must be an opening.

#2 there must be a pressure differential across the opening for air to flow.

So you have one of two things, you have pressure problems within this piping system or you have pressure problems in the building system.

I guess you need to get some pressure testing equipment in there and find out which it is.

The last sewer smell in a upper bathroom I dealt with was due to that subdivision’s treatment plant fault. I would have thought the traps would have kept the smell out, but it did not.

Tyler, did you smell it also (from the drain) or did you investigate based on claim of smell?

I ask because my first thought was the Water heater.

Is the P-trap at the proper depth? If the water is dropping too far (24" max.)/draining too fast it may be causing the P-trap to not have enough water in it for a proper seal. Slowly pour some water down the drain and see if the smell goes away. Along with this, is the vent the proper size, (not too small), which would also contribute to siphoning.

I agree with Jeffrey one other thing that can happen is too steep a slope in the basement forcing to much removal of water and leaving behind s h i t.

How often do they use the shower? P-traps dry up without use.

The trap seal is ineffective. Among all of the previously listed potential-causes, a clogged vent will allow other fixtures to pull the p-trap dry.

Thanks for all the input everyone. When I look down the drain, I can see water sitting in the P-trap. The shower is used every day so I dont think its drying up. This is on a second floor bathroom so the drop before it hits the trap cant be over 10 inches. The smell is definately coming out of this drain. The only thing that I can think of is the smell coming out of the weep holes where the liner ties into the drain, and there is something inbetween the concrete and the liner. Does that make sence?


Call a different Plumber

Have you used a Test Ball yet to confirm? If you suspect the mortar bed below the tile (however unlikely), you could systematically lower the ball below the weeps within the drains to isolate… I would suspect that it may be a good idea to get the plumber that worked on it before you did too much as well… wouldn’t be fair to tinker around with stuff and then point a finger.

I also suspect that if I went out and isolated that a smell was in fact coming from the drain, I’d likely want to have the vent and drain scoped as well.

Good luck

Make sure that water is not being siphoned from the trap when other drains are operating, especially the commode. Trap can still contain water and not maintain a seal if it drains past top dip.

I would plug it temporarily and see if the odor persists. If it does persist, look for other sources such as a disconnected vent in the wall, etc. If the smell stops, you know you are losing the sanitary seal in the trap.

Then I don’t see how in the world an odor is coming from that drain. Where is NASA when we need them?

Joe, he may see water in the trap, but is is vurtually impossible to see if the level is high enough to make an effective seal. My above post recommended pouring water into the trap to insure it is full, and check for odor.

Good point. Thanks.

PS, stop eating beans for week.

This might seem far-fetched but I had a similar problem…

slab on grade home, shower pan, tiled floor , Very hard water. pvc drain

The odor only happened when I used head and shoulders shampoo. I only used it occasionally so it took a while to figure out what the smell was. The smell would linger for days, and drive my wife nuts. The smell was close to sewer gas with a hint of sulpher. After a few more experiments (didn’t happen in the main bathroom tub only the shower with the the shower pan) I quit using the product. No more odors since

Essense of peppermint down one stack at a time. At the drug store. Seal the drain and test whether it is comming from somewhere else. You will be able to completely isolate where it is comming from.
It is possible that it is a bad connection at the wax ring…sound unlikely…it happens.
Very easy to do and will absolutely find the problem. It solved a similar problem in a busy restaurant.

That’s great advice Marvin. Where did you learn that trick?