Texasguy

We live in a double-wide, out in the country. We had a new septic system installed about Christmas time, the old system had a "failed field"...
The old system had the tank about 60 feet from the house and, when they dug it up, the drain line from the house to the tank had a "dip" in it that trapped water.
The new system has the tanks installed about 5 feet from the house and now we get a VERY strong sewer gas smell out of the roof vents of the house. I realize that to=hose vents are supposed to vent gasses and such, but the wind blows that smell right into the yard and it STINKS!
I talked to the installed and he can't explain why it smells now, nor could he suggest a cure. I think it smells now because there is no longer any traped water between the house and the tank.
I was under the house last week and noticed that there is room under there to put a trap of some sort to capture some water and prevent the septic tanks from venting out through the roof vents. I could build a "P" or "J"" trap from 4" pipe to trap some water.
Three questions:
Would this be legal and/or smart?
Would it work?
Would it cause drainage problems with the toilets, etc?

glennjanie

Different states have different plumbing codes. In some states a "main building drain trap" is even required. (In Kentucky we don't double trap anything) Yes, it will work for what you want. I can't advise on whether it will cause trouble; we Kentuckians believe it will but not everyone agrees with us. Logically, if you didn't have trouble with the sag in the line, you shouldn't have trouble with the trap.
Glenn

manhattan42

Glennjannie is correct.

A house trap would solve the problem but whether it is legal is up to your local plumbing code authority.

International Plumbing/Residential Code does not allow house traps except with the approval of your local code office.

There are sometimes ways to mitigate the problem without a house trap.

If your main vent is located to far down the slope of the roof, you can get this sewer gas effect by downdrafts blowing across the roof.

One solution can be to extend the height of the main vent so that downdrafts no longer affect it, but this can be unsightly...Or relocate the vent to a higher portion of the roof where downdrafting is unlikely to occur.

Personally, I'd go with the housetrap.

Texasguy

I don't know that raising the height of the vent will help, we have an "almost constant 10-20 MPH wind from the south here, and the back yard is on the north side of the house.
Thanks for the replys, I think I will just build a trap.

Mudball

Im not trying to take away from this post but I still have a chance to install one of these P traps (new install) because Im not done with the ditch from the outside of the house to the septic. I believe the roof vent pipe has two purposes which is to allow air to come in so the water can properly drain and so that gases can also be expelled...right ? Anyway if I put a P trap lets say between my cleanout which is about 12 feet from the outside edge of the house and the septic tank then when or if the cleanout is ever needed to be used toward the septic then wouldnt the P trap create a problem for the cleaning snake ? And I certainly dont know what Im talking about when it comes to plumbing but it also seems to me in my mind that the P trap would hinder the air/flow of fluids between the vent and the tank ??? But I guess the fact is that these house P traps are in use and do not cause any problem...right ?
Im just considering the thought installing one while it would be much easier to do so.
Thanks

manhattan42

Mudball,

If you do install a house trap, it needs to go immediately inside the foundation wall where the building drain exists the foundation, or immediately outside the foundation....or some other approved location.

Cleanouts need to be made available immediately at the house trap.

Again, check your local plumbing codes to see if a house trap is permitted (they are usually not permitted as glennjannie already indicated) and where they must be located if you do receive permission to have one...

Mudball

That sounds great manhattan42. Thanks for the advice