Stinky Septic Smell Mystery

[Brichards]

Good afternoon,

I posted this in general versus septic because I have no idea what the root cause of a sewer/septic smell is in my house.
Here's the explanation...

Moved into a 10-year old house about a year ago (unknown how long it sat vacant, believe about 4-6months).
- Septic System
- Water Softener
- Well Water (with pump and pre-pressure tank)
- Propane heat.

Shortly after moving in, noticed a strong septic/sewer smell in the basement. Couldn't trace it to the root, and it does not smell like it is coming from any drain.
After a while it starts to make it's way to the main floor of the house. Faster now that its winter, presumably because I am running the furnace?

Here's what I have tried to get rid of it, or related changes.
- First though it might be a propane leak because the smell is kinda eggy. Had gas company out, they found no leaks.
- Ensured all drain traps had water, and do so consistently.
- Basement has open drainage pipes that go to an empty pump-crock. Basically for the addition of a bathroom. It doesn't feed into the existing system, but I capped the open drain pipes and sealed the crock anyway.
- Had Septic tank pumped.
- Ran Bio-Clean and a bunch of other septic products.
- Snaked all of the drains and the septic vents (put the caps on the vents that keep leaves and animals from clogging them). None were clogged.
- Cleaned water softener components and ran cleaner through it.
- Replaced groundwater pump when it went bad.
- Replaced water heater anode rod (it was all used up).
- Replaced Furnace humidifier.
- Replaced pre-pressure tank.
- Had smoke test completed on the entire system. No leaks, vent stacks were clear.
- Found a nest of deceased mice in my furnace, on the burners, this year as I was inspecting before winter use. They had crawled in through the exhaust vent. Put metal grid over the vent outside to keep animals out.

So at this point I am totally lost, and not sure what to do. When I have the local plumbing company out, it costs hundreds of dollars, and I have yet to get a solution.

I have combed many forums about septic/sewer smell and not found anything that I haven't tried.

Here are the hints I have.
- Seems to be worse in cold weather.
- Vent stacks outside seem to omit a lot of septic gas. More than I would expect.
- There aren't any water usage patterns that seem to cause it to happen.
- Only myself and one other person live in the house.
- If I keep a window in the basement opened about 3 inches, it keeps the smell at bay. If I close the window completely, the smell starts to come back within minutes.

Any ideas would be very much appreciated.
Thank you for taking the time to read about my issue.
Happy Holidays!
Blake

 

[SlowDrip]

Wow, sounds like a doozey. since a basement window seems to help, it is most likely that the smell is being caused by something in the basement (which is a pretty obvious statement). My question would be, what kind of basement is it and what plumbing fixtures are there?

Is it a finished basement? If so, is it dry walled, plastered or something else? Is there a bathroom or laundry room or anything else plumbing related in the basement?

 

[Brichards]

Hi Slowdrip,
Thank you for the reply!

It is a basement that is NOT finished. The water comes into the house and the well pump switch is down there.
- Water Softener
- Water Heater
- Furnace (with humidifier)
- Ground water sump pump
- all of the water pipes (copper)
- all of the PVC drain pipes.

Laundry and all bathrooms are upstairs.

It is only a single story house with the basement.

Thanks,
Blake

 

[SlowDrip]

Hrm, well that rules out all kinds of stuff that smells like sewage but isn't, which I suppose is a good thing. you have already ruled out all of the common problems I am aware of.

I live in the city and haven't done any septic work since I was a kid since I now live in the city, so it is more likely that one of the other guys will have a better idea than I. The only thing that immediately springs to mind is that if you have improper bed drainage it may be seeping into the ground water and showing up in your sump pit. Of course, if your sump pit is dry then that kind of rules that out.

 

[Brichards]

Thank you for the ideas. The sump pit doesn't smell unfortunately. That is the real challenge, because it seems impossible to find the source of the smell. I believe that it smells like it is coming from the drainage PVC lines, but the smoke test ruled out a leak.

Blake

 

[SlowDrip]

Ok a couple other uncommon but possible ideas.

1) Is your sump vented? Sometimes people will tie a sump vent into the main house vent (which is wrong wrong wrong) which can cause back pressure on the system and draw stinky air through the vents. An indication of this is if your toilet bubbles slightly when the sump engages.

2) Does your air conditioner condensate line run into the drainage system at all? If so it should be trapped and vented. Yes, even this little line. Same goes for the furnace humidifier line. It is common to just string these lines to the nearest drain, but if that area is not trapped and vented a stench can come back through the lines.


The only other thing I can think to do is to hire someone with a handheld gas detector to go over all of your pipes in minute detail. This is even better than a smoke test in some cases.