septic smell from vent and washer

[Philodog]

My house was built in 2009, has a septic system, and since new there has been a septic smell from the vent pipes on very still days. Strong enough that you don`t want to be outside. Filters helped but now we are getting a very strong septic stench in the laundry room only when the washer is draining as if the gas is coming up the p trap when the water rushes by. The washer is a front load LG and I know they have had smell issues but this is definitely septic, not mold or gunk. I know the vent pipe smell may be unavoidable but the washer smell should be. Attached is a pic of the washer plumbing. It passed inspection but does everything look right? Could the septic system have been installed incorrectly allowing the gas up the pipe? Any other ideas? thanks!

 

[Smooky]

Instead of a sanitary tee it looks like they used a combination wye and 1/8 bend fitting. This will cause the p-trap to siphon dry each time enough water is put into the drain. The drain inlet looks too low in relationship to the trap arm height also.


http://www.ci.hillsboro.or.us/building/Images/washingmachinerough-in.JPG

http://inspectapedia.com/plumbing/1632s.jpg

 

[Sponsor]

 

[Philodog]

Thanks Smooky. Very informative pics. It does look like the drain inlet is too low. I don`t see an 1/8 bend fitting. Here`s a close up pic. If it just has the wye and/or the drain inlet is too low would this still cause siphoning ?

 

[Smooky]

Yes I think this is your problem. The proper name for that fitting is a long turn tee wye. That same fitting can be made with a Y and an 1/8 inch bend. The fitting that should have been installed is called a sanitary tee.

http://www.lowes.com/pd_22762-137-C...+dia+abs+long-turn+tee+wye+fitting&facetInfo=

http://www.lowes.com/Search=2+in++d...ewSearch=true&Ntt=2+in++dia+abs+sanitary+tee#!

 

[Gary Swart]

I believe the problem is not so much the wrong fitting, but you have an illegal S trap. To avoid an S trap, the vent must come off of the trap arm before it makes a downward turn.

 

[Philodog]

Thanks Guys. Gary, you said "To avoid an S trap, the vent must come off of the trap arm before it makes a downward turn." I`m not picturing that clearly. If I put in the sanitary tee straight out from the trap arm (like in Smooky`s pics) will this avoid the S trap? And do you think I can get away with having the drain outlet too close to the trap arm height like Smooky pointed out? That would allow me to use the existing hole and not have to drill through those three studs.