I have had an issue with a sewage smell for a while now. Its real bad after a shower and only comes through the hvac duct work. I can smell a little in the laundry room which has alot of our plumbing, a sump pump pit, tankless water heater, and furnace along with the air handler. So I know the intake of our a/c has to be pulling the smell in and spreading it throughout the house. I didnt a smoke test (knowing I was doing it wrong) through the drain vent didnt plug anything shot smoke through and it came out of ever vent in our house and no where else. My question is has anyone here ever came across this? Thanks in advance!