I have been reading about others who have unidentified pulsing in their home. We too have this pulsing/humming problem. We've tried everything to locate it. I will try the ballcock replacement in toilets. But the other suggestion on this website was to open the "sewerage outlet". What is a "sewerage outlet" and where is it? We live in the city and have city water so do we actually have a "sewerage outlet"?