Sewer smell from drain but only when water is running?!

Help Support Plumbing Forums:

MRubenzahl

New Member
Joined
Nov 27, 2021
Messages
4
Reaction score
0
Location
Kenoza Lake, NY


When the shower is on, sewer smell comes up from the drain. I can't figure it out! Clues:

  • It only happens when the water is running.
  • No other drains (bathtub, sinks) in same room or elsewhere do this.
  • It's a rural home with septic system, about ten years old.
  • For years, the shower was very low flow but when I got here, I fixed the flow (a defective washer was plugging the shower head supply hose) and I think that's when the smell started.
  • The shower drain pipe goes straight down for about 7 feet, then there is a trap, then a horizontal run where it joins other drains on the way out.
Any ideas? I am stumped!
 

Twowaxhack

Professional
Professional
Joined
Feb 9, 2021
Messages
5,749
Reaction score
2,591
Location
United states
It grows stinky stuff in the vertical drop.

You could move the trap higher and use a studor vent to protect its trap seal.
 

MRubenzahl

New Member
Joined
Nov 27, 2021
Messages
4
Reaction score
0
Location
Kenoza Lake, NY
Thanks, @Twowaxhack for your expertise and insight. Next step is clear: Call a plumber with your level of expertise. Hope I can find one (I am in a very rural area).

I think I can rule out gunk in the pipe above the trap, since the smell is only while water runs. I appreciate your guidance about the long run above the trap, which explains why the problem started when I fixed the flow problem. I am thinking it also might be a venting issue. Studor vent might be the remedy or maybe vent is wrong; and raising the trap would be great but I don't know if the house construction makes that area accessible.

Regardless, now above my pay grade and I will summon the pros!
 

CT18

professional
Professional
Joined
Apr 30, 2014
Messages
978
Reaction score
370
Location
Bloomfield Hills, Michigan
Yes the longer drop can pull a siphon on the trap. I am currently dealing with the same issue on a large project for Amazon. The inspector is letting us exceed the 24" max only on the floor drains for the Air Handling Units.
 
Top