Odor because 2nd trap?

[Alexander Phillips]

SEPTIC ODOR COMING BACK UP THROUGH ONE SHOWER DRAIN.
I have two showers going into the some outgoing pipe. Shower 1 drains into a pipe with a trap. That trap goes horizontally to where shower 2 enters a foot or so down the line and then shower two drain pipe enters. Then there is a 2nd trap. Shower 2 has no problem with odor. Shower one does. I tried using one of those interior exhaust caps (with that snorkel like stopper on top) along the line near shower 1 drain. It made no difference. It is worse if I wait 24 hours or so. I know that means that water has probably evaporated in the trap.
but there is no odor until water is turned on and going down the drain.

 

[johnjh2o]

What you have are running traps. They do not meet code just for the problem your having.

 

[Diehard]

2 traps of any type, in series is against most codes. I say most because there are still a few places that require the old house traps. In which case a vent must be provided just upstream of it.

The double trap causes drainage issues because air becomes trapped between the two traps and air is lighter than water. This causes the air to want to travel up as the water flows down which can result in no drainage.

A vent between the traps allows the air to move instead of becoming trapped.

But that explanation doesn't clarify why you would be getting sewer smell back thru drain #1.

As John pointed out, what you show are not even P-traps but are running traps. I question if that's actually what you have?

I also question if what you show is exactly what you have? Typically a shower trap is located directly below the drain although it doesn't have to be.

It doesn't make any sense to me that you don't get fumes coming back into shower #2 . Where else would the fumes in shower #1 be coming from if not thru that farthest downstream trap? That's why I must question if you have the piping shown exactly how it is.

 

[Alexander Phillips]

What you have are running traps. They do not meet code just for the problem your having.

/ So what if I ran a direct line (took out Trap 1)? Do you think that would make a difference?

 

[frodo]

 

[Diehard]

 

[Alexander Phillips]

View attachment 22092

@ Macgyver - Thanks for the heads up. I'm trying to figure out a way NOT to have to put another hole in my roof running another vtr. Do you think it's ok if I tie it in somewhere where shower 2 is tied into the roof vent I already have?

 

[Alexander Phillips]

What you have are running traps. They do not meet code just for the problem your having.

I hear ya. thank you.

 

[frodo]

yes,, tie the vents into another vent in the attic
that is perfectly acceptable