We finished our basement and had extensive plumbing done in the
process, not only inside, but also outside. After our most recent
work (we had a pipe installed to evacuate our washing machine water
that was between the sheet rock and the wall -- it froze this winter.
The plumber re-installed the line on the warm side of the sheet
rock.), we notice that when we do a load of laundry, we got the odor
of sewer gas or methane eminating from our laundry tub. Any ideas
what could be causing this? -- it's very frustrating. Thanks.