OK, here is a problem that has been bugging me for some time. The floor drain in our laundry room, which has a concrete slab floor, is normally odor-free. I make sure that water frequently goes into it (and I think the washing machine drains into the same pipe just past the floor drain, too) so it is not a dry pipe. But when we turn on the attic fan, a bad (sewer gas?) smell starts issuing from the laundry room. So it takes a negative-pressure system to pull this smell out from wherever it is coming from, I suspect the drain.
Anybody have a fix for the problem? We really can't afford to have the whole shebang dug up and re-laid, is there a DIY repair or a quick fix I could do? I have had limited, short-term success with putting vinegar water down the drain.