We had just finished installing a basment bathroom when sewage started backing up into the shower stall. The bathroom had been in the works for some months and there was no sign of anything like this from the pipes while in progress. I called the plumber who dissmissed me not so nicely but did recommend Dave Harding from Scotty's. He came over the same day and was friendly and relaxed. After walking around our basement and looking at all the pipes we had and what was where, he had it narrowed down to the one direction valve in the sewage exit pipe. Once he uncovered it, sure enough the flap had broken (it was VERY old) so anything with solids were backing up, but the laundry water flowed ok. He had it fixed, cleaned out and running well in less than half an hour. Huge relief that we didn't have to start tearing up the brand new bathroom!!