What could cause a sewer gas smell coming from the drainpipe where the washing machine drains when using the machine Washing machine is on second floor Plumber check drain pipe and OK?

Answer 1

Your dish washer has a 3/4 or 1 inch drain hose coming off of it and connects to the sink drain pipe just above the trap. In new construction, the trap should be a P trap in that it goes directly into the wall cavity and down into another pipe that goes to the septic or sewer. But where it goes down another pipe should also go up and out through the roof as a vent. If you have old construction you may have an S trap where your drain pipe goes directly down to the sewer without a vent. So to make a long story short, when your washer drains it is sucking the trap dry. Or your vent is cloged, or I might be wrong altogether

Answer 2

There is usually a trap--"U" shaped pipe on all drains that stays full of water to block gasses from coming in. It could be the trap is not staying full of water. It could also be you're pipe is dirty. It happened to our washer drain a few years after we installed. We dumped a bottle of draino in then did 3 or 4 washes with a normal to high bleach content and that took care of it. Hope that helps-Disclaimer----took me 10 minutes to wire my dishwasher-6 months to get the courage to plumb it.

Tom