We have been in our house for 2 years now. We have 2.5 baths upstairs and 1 downstairs. When we flush the toilet downstairs, we get a sewage/septic smell outside. It's brief, but don't use the downstairs toilet while we out on the back deck! We pumped septic after we bought the house, just because I had friend with a pump truck. Pumped again last summer, didn't need it per my friend, but we had the smell. (Still do.) Now, in the crawl space I can determine where the bath sink, the shower drain, the toilet, and even the drain from the laundry connects, and have traced the pipe to the main discharge out to the septic. We only get the smell with the toilet flushing. Not with the shower, or sink, or laundry. Any ideas on my next steps before I get a plumber who wants to do a never ending "check and see". Thank you.

 

No smell in the crawlspace when flushing that toilet ?

 

Honestly, I haven't staged myself to be under there yet when it is flushed and if I'm not under there when we do flush, no scent by the time I get down there and it is fine deckside too. I do know that all pipes are in crawlspace, until they go underground right next to the septic tank. I'll give that a shot shortly.

 

[QUOTE]didn't need it per my friend [QUOTE]

Ohh, maybe time to get a new friend!

So that makes sense, shower/sink is gray water no stink, toilet is, well, you can figure.

If tank was pumped and smell still happens you have a field issue, possibly leaking or saturated!

You don't need a plumber, you need a septic company to evaluate the situation!

 

I understand regarding gray water and toilet being different, yet all drains connect and lead to septic...and when the other toilets flush, no odor. I do believe the scent us in crawl space and there is a crawlspace vent near the piping from that side of the house. I think the ventilation pulls it from underneath there to underneath our deck and that is why we get there scent in the deck area.

 

Wumby-

Never tried this myself, but is it possible to run a test from each fixture where you would add some kind of liquid to the water with a real pungent (but temporary) odor and kind of do a trace? Seems like that could be done - but I guess since I never heard of that test there must be something wrong with it.

Also, did you check to see if somehow water was being sucked out of the trap in the downstairs toilet? I think that would cause a bad odor.

 

In regards to a test. I'll run the shower only and no smell. I've waited for laundry to drain from washer, nope. Bathroom sink, left it on and no. Just toilet. How could I check to see if trap is getting sucked dry and hiw would I remedy that?

 

The smell is likely coming from a vent on the roof.

 

I just meant if you look in the toilet bowl and it’s dry, the odor would be coming from there. But I think if that happens that would be something like a vent problem that would cause the trap to be sucked dry.

But as Tolyn says it’s probably a vent problem. I have read that you can get odors from the vent even depending on the time of year or on the wind outside.

 

Roof vent. Ok. I am going to prevent the flap from closing in a little while crawl under the house and see...well smell. If nothing, then I'll suppose roof vent. If that's the case...2 story steep pitch roof. I wont go up there. Should I get a plumber out t ok clean it out?

 

The only way I have heard of to do it yourself is to put a hose down the vent. But that’s out in your case, if it’s much too dangerous to access the opening. Not worth getting injured. So the only thing I can think of would be to have a plumber do it. Maybe one of the other guys would think of something better.

 

Some septic setups have a vent on the side of the house in the foundation. It's a vent on the house-side of the main trap. Do you know if you have a main trap before the pipe leaves the house to the septic tank?

Sometimes the trap gets clogged and needs a cleaning.

 

I do not know if I have that trap. Let me google what one may look like and then do some investigating.

 

Some where between the septic tank... and your house, where the line exits....there could be a vent pipe sticking up. Maybe it used to be capped off and now the cap is gone ??

 

Ok, so. Today there is no breeze and humid. Thought it would be good opportunity to double check some of my troubleshooting. I have not found a trap in the drain line. I've chased it from that bathroom, figured out all the connections and it goes to the corner of the house where the septic tank it. The lid to the septic is approximately 10 feet straight shot to where the pipe, with a clean out, disappears into the foundation bricks. Now, I ran that shower and noticed I do get the smell with the shower running too. No smell in crawl space, but outside. Steps go down into a flower bed with an additional step down into the yard right above the area where the line goes from house toward septic lid. So, smell doesn't seem stronger on that corner outside than it does 20 feet away sitting on deck. I'm wondering if I have a septic vent pipe somewhere underneath the deck? Underneath the plastic that is laid down to prevent erosion from rain (slight downhill toward septic side of house). Don't know where the vent pipe would be, nor can I determine whether I have a trap between foundation and tank itself. Suggestions for next steps? I'm leaning away from it being stack on the roof, stack is on other side of house directly above the bathroom.

 

All the septic systems I've seen have a vent like this on the outside of the house. It's part of the house trap, a U-trap just before the pipe leaves the house.

But maybe it's regional and not used everywhere.

 

...nope, can't find one of those. I'll have to wait until this evening to pull some of the lattice off the deck and crawl under there and inspect things under the plastic a bit more too.

 

I haven't seen a house trap in years. I don't know why a house trap would ever be required if the house drainage system was installed properly with each fixture being individually trapped. I suppose it could be different with a septic system, but I cannot think of a single reason why it would be necessary.

 

Dont have a house trap. I'm wondering if I have a partial blockage between house and tank that forces the gasses out. Just think I'll pull a plumber in to troubleshoot too/clear out at that main clean out port near the tank.

 

I had a vent pipe on the septic tank that gave off a smell. Read about filters for it, but decided just to cap it off and see what happened. Smell went away and I've had no issues with the system, that was almost 10 years ago. It was a new dosing system that had been installed just prior to me purchasing the home.

 

Thanks, but I cant find a vent pipe.