Hello, I can relate to all these smells and problems with these nasty smells, none of the "remedies" worked for me... I eventually replaced the vent valves on the vent pipes that are located under the kitchen sink and bathroom sink.. These valves are on top of a black pipe and screw off, I got good USA made replacements in the plumbing department at Home Hardware, The rubber flaps were distorted on the old ones.. I thought I'd won the battle, but the smell came back, tracked it down to a storage cupboard that had the rough plumbing for a washer/dryer in the back behind a panel. The vent valve at this location was missing it's rubber flap completely, after another visit to Home Depot for the third new valve, all smell problems were cured, Hope this helps, Gerry
