I noticed my laundry room has developed a strong sewage smell over the last two days. I suspect it may have to do with vent blockage, but I ran a garden hose to the vent in the roof last night and had my wife listen near the drain in the laundry room, and she reported hearing a slow trickle of water - so it's not completely blocked up.
- I haven't washed anything particularly dirty that might put a lot of debris down the drain pipe recently.
- The washer has been used regularly, so the drain pipe trap shouldn't be dry.
- I'm on a septic system, if that matters. None of the other bathrooms or sinks in the house have any smell coming from them. I sniffed all the vent pipes while on the roof and could detect a faint level of the same laundry room smell coming from all of them, but I think that's normal.
- I checked in the attic and discovered the vent pipe makes a 15-20 foot horizontal run before exiting vertically through the roof.
- The slope on the horizontal run actually dips down and back up a few inches over its distance, but the issue just surfaced after living in the house for 7 years. I suppose it's possible it's acting as a trap for venting gas, but I don't know why it would start doing so spontaneously. (The water I ran down the vent from the roof before noticing the lack of proper slope could easily exacerbate this possibility, so I plan ensuring it's drained tonight.)
So my forward plan tonight is as follows:
- Snake vent pipe.
- Pour water down drain pipe to fill trap if it's empty.
- Cut vent pipe in the attic and snake down into drain pipe from there.
- Reroute attic vent pipe to have a minimum 1/8" per foot slope at all points.
Any other suggestions for remediation?