Ranch home with large 2 sink, shower, and toilet master bathroom. Only when it gets cold out, I have problem with backup of septic gas. I live in FL.
Toilet is vented to roof. Roof vent is clear. Is it too short? Do I have a sewer line break? Bad seal on toilet? Ordor seems to come from sink and shower area? Odor only bad when its colder out. Help. KLG:(

Most bad smells from showers and lavatories come from rotting hair matted in with grease in the drain lines. Try this for the smell. Tonight before bedtine Take a gallon of bleach and pour half down each drain and let set over night. Next morning ,(and this is important) flust out esch drain with two large pans of boiling water to loosen the grease and flush the mess out.
Also, pull the lavatory stopper and look down the drain. About 4 inches down you'll se a small rod sticking out. Fish out any hair that's caught there. This should make your drains smell better. If the smell still persists after that then click on back and we'll discuss capping the vents with a backdraft cover. Regards, Tom

Hi Speedball,

Thank you for your quick response. I have tried putting bleach down the drains but nothing really improved. This is a serious sewer gas odor that ONLY comes when its cold outside and warm inside. We in FL. Have just been hit with colder nights and the smell is horrible. Maybe a pressure difference with the colder temps makes the vent pipenot draw properly.

Could the problem be poor draw on the stack vent pipe and maybe I should make it longer? We have only one vent pipe on the roof which vents the toilet. I don't know if the sinks and shower are tied into that. Or, could the problem be a poor toilet wax seal and when the former owner added tile, the flange doesn't meet properly with new floor height? I'm driving myself a little crazy trying to figure this one out. But, the odor right now is terrible.

I don't want to even think of a broker line problem since it only happens in winter.

Thanks, Ken

Hi Ken, I live in Sarasota. So I'm extremely familiar with Florida plumbing. Sewer gas raises in warm weather and descends when it gets cold so you smell it more in cold weather. If it smells worse around the base I would check that the wax seal's doing it's job. Regards, Tom

Hi Tom (Speedball 1)

I examined the vent pipe on the roof over the toilet in the master bedroom. It is only 5 inches high and quite narrow and is below the top area of the roofline next to it. Would a higher pipe draw better? Should I extend it?

The odor seems to come out more in the area of the two sinks than the separate area for the toilet. Sometimes it comes out near the toilet but most often, 6 feet away near the sinks. Do the sinks need a separate vent pipe to the roof. How do I know if they are tied into the toilet vent stack? Can I add another trap to the sinks?

I can't believe I'm spending a Saturday night writing about sewer gas?? Ha! Oh well... thanks again for your info. If you are so inclined, call me on my cell phone 239-877-3777. Do you make service calls to Marco island? Ha!

Thank you so much, Ken

Can I add another trap to the sinks?

No you may not. It is illegal according to virtually all codes to double-trap a fixture.

I doubt Tom would make a "service call" - in case you haven't read his profile, he's retired. Like Tom said in this post (https://www.askmehelpdesk.com/showthread.php?p=48640#post48640), "My service calls consist of sitting on my duff and instructing you to do the dirty work" :D

If I may offer my humble opinion: if the smell is coming from the sinks, it sounds like the trap (or traps) is not doing its job. I can think of two possible reasons offhand for this: a) if your house is really old, you may have an S-trap instead of a P-trap or b) the sinks are not properly vented or the branch vent for the sinks is somehow clogged. In either of these two cases, since there is no air entering the drain line after the trap but before the first vertical drop, it's easy for a siphon to develop, which would suck all the water out of the trap, leaving an easy path for the sewer gas to enter the room. As for why you smell it during the winter, well like Tom said, cold weather makes the gas descend, making it more noticeable.

So for starters, check what kind of trap you have. If it's not an S-trap, try to find out how the sinks are vented.

Either way, keep us in the loop on this one.
Moishe