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

[MRubenzahl]

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!

 

[Jeff H Young]

The vertical off the trap being 7 foot I think max code is 2 ft . certainly a very unusual way to plumb it. no gurgling on toilet? where's your clean out?
I'd cut that 2 inch wyeing off and run shower and see if there is a back up if not put shielded coupling on. This test takes less time then posting the idea .
But I think your system is poorly plumbed, never seen a trap so low and expect its siphoning out the seal . since I've never seen or heard of trapping in such manner I suspect that or a stoppage

 

[Sponsor]

 

[Reach4]

Toilet flushes fine? How about 3 times in a row?

It's a rural home with septic system, about ten years old.

Pumped how long ago?

 

[Jeff H Young]

Good chance he has back up . determine if its backing up look down a clean out? I'm thinking its backing up but wouldn't trust my date of last pump to be of much help in determining it. A failed septic system could be problem or not.
how long after you repiped your DWV did this problem start

 

[WorthFlorida]

Do you know where the vent is? I see none in this picture unless it's the sink drain pipe. Seven feet it way too long and the as the water drains too fast it is siphoning the water out of the trap. Jeff is correct that 24" is the max vertical distance. After a shower slowly run the water to fill up the trap. Poor venting will push air back up toward the drain to make room for the water, usually its when you hear gurgling.

How is it 7 feet? On what floor is the shower. The wood looks fairly new, how old is the home or is this part of an addition?

If you google, this statement is the horizontal run, not the vertical.
How far can shower drain be from P-trap?
The maximum distance from a shower trap arm to a vent is usually 5 feet, though some municipalities may allow up to 8 feet.

 

[WorthFlorida]

 

[Jeff H Young]

Perfect vent right next to the trap . No issue

 

[Reach4]

good chance he has back up .

If he has not pumped the septic in the last ten years, this symptom could be a blessing/wakeup. Pumping late can be very expensive.

A plain old blockage before the tank is important but not as critical.

On that plumbing, I would like to see a photo from under the toilet area looking up.

Regarding "what is this", maybe that picture from beneath the toilet area could include that. It does not ring a bell with me.