Got one of these fitted on bathroom sink downstairs. Rotten egg/sewage smell coming from sink for some time now. Sink isn't blocked. Had a plumber out who cut some pipe off waste pipe (floor end) as pipe was bit bent and water had been backing up and leaking at base for a while. Leaking has stopped but smell is still there. Is it possible faulty straight through pedestal trap is causing smell leak? Plumber seemed to be adamant it wasn't that as it wasn't a p-trap.