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flyman
Mystery septic smell in shower

This one has me puzzled. When we take a shower in our first floor walk-in tiled shower we get a septic smell from the drain. The house is only 4 years old, the problem started about 1 year ago, is intermitten and most noticeable in the winter. I inspected the shower drain trap in the basement and it appears to have been installed correctly. The bottom of the drain pipe from the trap is 4 inches higher than the bottom of the trap. Is it possible that something could cause the water in the trap to be siphoned off? There are no problems with any other drain in the house including a second floor shower, everything drains ok and our septic system appears to be operating OK. I'm about to call a plumber but I'm not sure they could solve the problem.

dj1
Re: Mystery septic smell in shower

Inspect the vent coming out the roof from this drain. It may a blockage.

johnjh2o
Re: Mystery septic smell in shower
midwest_builder wrote:

The bottom of the drum trap could be filled with hair preventing the proper amount of water to remain to block the sewer gas. Yes, siphoning is a big problem in some situations. Is there a bathroom above this area whereas both rooms are tied into the same common sewer line? Nothing wrong with that, but could be perhaps pulling gas from above. Also, are you sure it’s sewer gas and not a hard water smell (rotten eggs)? This is often the case in a smaller enclosed shower where the air circulation is very limited.

Drum traps haven't been used in a good many years. I doubt they have one. Sewer gas doesn't go down it goes up. If there was enough hair in the trap to prevent it from filling I'm sure the shower wouldn't be draining. Take a look in the trap and see if you see standing water. If you do the trap is not siphoning. If there is no water in the trap then you have a venting problem. Or it could be as dji stated a plugged vent, it could also be not vented at all. I would need a picture of the piping to determine that.

John

flyman
Re: Mystery septic smell in shower

Thanks for the responses. I was thinking it might be the vent but wasn't sure how it would affect the drain. There is a vent on the bath roof as it is a one story part of our two story house. I'll get up on the roof and check it out.

dj1
Re: Mystery septic smell in shower

flyman,

You need a cam inspection. A visual inspection won't reveal much. It's possible that you will need to snake the vent too.

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