I'm on septic tank and once in a while would get a little sewer smell in the house that would seem to poor or linger in the hallway between bath and bedroom or in the utility closet that opens into the bedroom but it would dissipate fairly quickly. Summertime now and instead of firing up old HVAC decided to put in window units in bed and kitchen. At the same time, had to completely replace 50 year old septic system to new high tech, high maintenance ridiculously expensive aerobic drip system. SO...all is good but when I run window units, I get a horrible build up of stench. It's not immediate as it takes a few to 10 minutes before the smell begins to permeate everything. I thought it was the a/c unit itself so hubs removed and cleaned, sanitized both units then reinstalled. Smell still occurring. Called septic company - they said plumbing problem. Called plumber who went under house and said there was a vent pipe not capped so he duct taped it up and there was another plastic pipe that look like it broke due to settling but it had a rubber boot over it that had slipped, so he pulled it back into place and taped it up too. He left and all seemed okay until that night when the smell returned after running a/c. There's no smell in the attic - but there is a smell under the house but not all the time. The vent pipe that runs up to the roof...it actually stops short and then there's another piece of pipe attached to the roof for it. In other words, the pipe is to short to actually go thru the roof and there's about a 5 inch gap. Could this be the problem forcing the vapors to down draft somehow and the window a/c's are sucking in the air beneath the house? If I extend that pipe and put a charcoal vent on it, would that solve the problem?

 

Hi wifey, and welcome to the forum. Not a pro on this but could you explain "The vent pipe that runs up to the roof...it actually stops short and then there's another piece of pipe attached to the roof for it. In other words, the pipe is to short to actually go thru the roof and there's about a 5 inch gap. " Not sure what you are describing. As a note, cold air as from those ac units falls to the lower areas of the house and leaks out (reverse stack effect). As it leaves the same volume of air enters near the top of the house. That can be from the attic or from air paths around plumbing vents or chimneys.

Bud

 

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Sorry I submitted without remarks - but the metal part is the pipe....it is too short to actually go thru the roof so they sealed a piece of pipe on top and I guess that has the gas vapor rises it would know to go out the roof pipe. lol Sounds ridiculous but house is 50-60 years old and find lots of creative things around here.

 

If that gap is open to the attic that needs to be fixed as it could be venting into the attic and then the house. The pros here will know what code wants to see but there are simple options to temporarily bridge the gap and test to see if it helps the smell.

Bud

 

Great info in explaining how the a/c air moves - thanks for the help - you gave me a place to start.

 

If he actually used duct tape, you need to find a new plumber. Duct tape is great for reattaching a bumper to a car, but has no place in plumbing!

It should have been capped with either a cemented on PVC cap, or a rubber cap like this


Also, if a pipe is cracked, I wouldn't rely on a rubber boot to fix it for any long period of time.

It sounds like you need someone to take a look at your plumbing and get it up to snuff! We can help of course, but it depends if you want to get into plumbing yourself.


Do you have any unused or rarely used shower, sink, or floor drains in the house? The traps can dry out after a few weeks and provide another way for stink to get in.

Do you hear any gurgling when you flush toilets and such?

And if you want more help, posting a few pictures can help!