Occasional smell from shower drain

[lbeachmike]

Hi there -

We are noticing very occasional smell from the shower drain. We've only noticed it at night, and days apart.

If this is backflow of sewer gases, should I still notice water in the visible part of the trap at that time? All other fixtures in the house are operating normally and do not have any evidence of odor.

I do notice the shower drain water looks murky, but I'm not sure if that is typical or not. Is it possible it is not sewer gas, and the drain needs to be augered, or would there be obvious evidence of a partial clog?

Whatever the cause, I'm perplexed why it is only happening occasionally.

Thanks.

Mike

 

[SHEPLMBR]

You may have a small blockage.

 

[pasadena_commut]

We are noticing very occasional smell from the shower drain. We've only noticed it at night, and days apart.

There is a trap under the shower which is supposed to block the sewer gas. If the trap dries out sewer smells may be evident. Normally it takes many days for that water to evaporate enough to allow sewer gases past, but if it is very hot, or there is a leak in the trap, that can happen in less time. If there is a blockage in your sewer line gases at higher pressure can be pushed back through the trap. When that happens the toilets also tend to have problems, like the water level changes for no obvious reason, or they bubble when somebody takes a shower. Also you will generally find yourself standing in a pool of water when taking a shower, at least if you take a long enough one.

If there is a clean out you can open do so and look into it while running a lot of water through the system. If it flows freely for a long time, and while this is going on nothing is backing up in the toilets, then you don't have a blockage. Conversely, if you are looking at standing water, or it backs up out of the clean out, then you do.

Is there access to the trap from under the house? If so, fill it with water, then go see if it is leaking. Those sorts of pipes sometimes are prone to condensation, so there may be crud all over the outside, or even on the bottom as if it was leaking, even if there was no actual leak.

 

[lbeachmike]

Thanks for this information. I don't believe that whatever has been going on is consistent with any of the possibilities you've described. I simply don't seem to have any of these symptom sets.

In fact, the only symptom has been the occasional smell, though I've now not smelled this since the post. It had occurred about 4 or 5 times and many days apart for the last two occurrences.

I've tested flushing the toilet beside the shower while watching the water level in the shower trap and I didn't see it rise or fall. Only a verrrrrry slight rocking motion.

Our main trap is located in the basement, so no visibility below it. It's a two-family house, so a lot of total fixtures, and no symptoms at any other fixture.

 

[pasadena_commut]

In fact, the only symptom has been the occasional smell, though I've now not smelled this since the post.

Is it possible that the smell was not from the sewer but from a bathroom elsewhere in this building, travelling by some other route? Out one window and in the next? Up or down a common ventilation shaft?

 

[lbeachmike]

Is it possible that the smell was not from the sewer but from a bathroom elsewhere in this building, travelling by some other route? Out one window and in the next? Up or down a common ventilation shaft?

Well, I investigated that and went to the downstairs apartment to make sure there were no mysterious smells emanating from there. It seems that it was isolated to the upstairs master bath, and it seems to have been coming from the shower though I was never perfectly certain.

I was unable to investigate the attic - given there are three recessed lights in the bath ceiling, I suppose that is still a possibility - but it would seem that if it came from the attic, it would have to impact other rooms as well so I sort of ruled it out.

 

[lbeachmike]

It turns out that this odor is occasionally coming from the steam vent of the 100 year old radiator in the bathroom. Usually the smell coming from the vent smells fine. But occasionally, it has a sour sort of smell like old pipe, which smelled to me similar to drain pipe.

Any plausible explanation for this? Particularly why this odor would only be there once in a while? The other radiators never have this smell.