Ask Me Help Desk - Smelly Shower Drain

Tom, Thanks for the idea. Over the past few weeks I've been tracking the odor by day/hour. The smell starts about 7 am and fluctuates but is is still present until sometime between 10 and 11 am. There is usually no smell (regardless of laundry, baths, dishwasher use) between 11 am and 4 pm. Then the smell starts up again and peaks around 6 / 7 pm. There have been a number of times where no one has been home for hours and no water has been used yet the shower still smells. If we run the shower the smell disappears and sometimes will be gone and sometimes will be back within the hour. My log has shown fairly consistent results with the exception of the past 3 days and the only unusual factor as far as I can tell is that it's been very rainy. Any thoughts?

To add to my previous post. If I run the dishwasher or washing machine during the peak times of the smell 7-11am or 4-9pm it sometimes causes a surge in the odor other times there is no apparent change. Thank you again for your thoughts!

Hi. We are still searching for a solution to our problem. We have ruled out a number of theories here and are pretty certain that the smell is coming from the drain. I have noticed that the standing water in the ptrap fluctuates an inch or more when the toilet is flushed and it also ripples and moves at random times when there is no water running in the house. What could cause the water in the ptrap to move? Thanks, Donna

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I have noticed that the standing water in the ptrap fluctuates an inch or more when the toilet is flushed and it also ripples and moves at random times when there is no water running in the house.

This tells me that the bathroom vent's blocked and is attempting to vent through the trap in the shower. Drawing the shower trap seal down every time you flush would explain the odor. Snake the lavatory roof vent. Put out enough snake to reach the base and 20 feet more. Then flush the toilet while checking the trap. I think you've located the source of your stinky shower drain. Good job! Tom

Thank you Tom! Would the blocked vent cause the water in the ptrap to move even when water is not being used in the rest of the house? I also am wondering if it is possible for something to be backing up from where the lines connect to the street. Our lot was originally one large parcel and was split into two. The other house which is located in front of ours has many rentals and over 10 people living in it. If all of these people were showering and using water first thing in the morning and in the evening would it be possible for some sort of surge to come up our lines? Just a theory I was wondering about. Thanks again for your help!

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Would the blocked vent cause the water in the ptrap to move even when water is not being used in the rest of the house?

Yes! Other drain would produce a suction that the trap would respond to.

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I also am wondering if it is possible for something to be backing up from where the lines connect to the street. Our lot was originally one large parcel and was split into two. The other house which is located in front of ours has many rentals and over 10 people living in it. If all of these people were showering and using water first thing in the morning and in the evening would it be possible for some sort of surge to come up our lines? Just a theory

Doubtful! If you had a sewer line surge you see in at the lowest point in your basement.
Snake the vent and see if "ole Stinky" goes bye-bye. Good luck, Tom