Sewer Smell
I have a family member that recently bought a 60s era town house on the BC North Coast. They have a sewer smell in their house, they say it gets worse with heavy rain.
It shows climate zone 5, but it is extreme coastal with +/- 9′ of rain per year.
Townhouse is sandwiched between units. Foundation is some form of concrete grade beams placed on concrete footing pads,the grade beam is not in direct contact with the ground, so there would be some interchange of air between neighbouring crawl spaces. Ground in the crawl is wet with some ponding at the lower spots.
I was in the crawl, and aside from the wetness (I would guess most every building in this area has similar conditions) nothing looked out of place. So no obvious source for the smell.
Things I have asked them about, and eliminated as concerns:
-dry traps that could be allowing septic gasses into the house
-floor drains
-open pipes in the crawl
I am assuming that the smell is originating in the crawl, and am coming up with a plan to install exhaust fans and put the crawl into negative pressure, to see if this helps. If the smell is coming from a neighbouring crawl, the neg pressure should make it worse, but then we will know.
Any other ideas, of either the source or a potential fix? Thanks!
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Replies
plumb_bob,
My guesses would be:
- Blockage or crack in a vent-stack above the traps.
-Crack in a drain in a location where it doesn't leak (a vertical section, or topside of pipe) which allows sewer gas to escape.
- Wax seal on toilet.
Thanks Malcolm, those are great. We replaced the wax ring on the toilet, but looking into the others makes sense. I guess we could get a plumber to plug the DWV piping at the top and bottom of the system and do an air pressure test.
Also considering if there is a leak in the sewer outside the building, and heavy rains saturate the ground pushing it up.
plumb_bob,
These are notoriously difficult to pin-point. You may well be right it is in the surrounding ground and smells worse when wet.
With the connected residences, damp floors and the odor correlating with heavy rains, I wonder if the problem is not actually in their unit but in a neighboring unit.
Also, I would push them to double check their traps.
I was there on the weekend to help paint, and had a quick look around, they did not notice the problem until after I left. I am now 400km away and helping by phone.
I feel playing with the air pressure of the crawl should help regardless of the root cause (if it is not a trap/open drain problem), we just have to be careful of unintended consequences.
Thanks for the feedback.
Plumb_bob
Check out this Youtube video. This is a service that is available in my area. You need to be sure that you use the right products to ensure you don't create smoke damage in the house.
https://www.youtube.com/watch?v=2IpLABJw2KU
If the problem is worse when it rains, it could be an incorrectly sloped vent pipe.
If the vent horizontal run in the crawl slopes the wrong way, water goes down the vent when it rains and if there is enough water in there it effectively turns itself into a ptrap when full. Then the rain stops, and it evaporates just enough to become a vent again....
Have them go into the crawl and check, with a level, the slope of any dedicated horizontal vent piping...
Very good point, I have run into this more than once. Vent pipes not graded properly or not supported in the middle causing a vent pipe full of water.