For several weeks now we have had a stinky situation. Every time a large amount of water drains in our house, such as out of the bathtub or washing machine, we get a sewer gas smell all through the house. We put up with it for a while but when it became apparent that it wasn’t going to go away on its own we called a plumber.
I thought it was a vent problem. When you drained a bunch of water you could hear bubbling in various drains, which is a classic sign of a venting problem.
The plumber at first thought that one of our old 1920’s era cast iron pipes had sprung a leak since there was a big puddle under the pipe.
Part of the problem was that the crawl space had so little clearance that nobody could get close enough to get a good look. Finally today we cut a hole in the kitchen floor by the puddle to see it better. We ran another bunch of water down the drain and nothing leaked into the puddle, and the water in the puddle was just plain water without any yucky sewage type smell. So we figured it probably wasn’t a leak issue.
Then the plumber ran an auger down the drain and said he cleared three different obstructions. We ran some more water and voila! no bubbling and no stinky smell.
The post-mortem theory: there was a partial block in the drain pipe. A small amount of water, such as from a sink or a toilet flush, wasn’t enough to be held up by the obstruction. But a large amount of water would back up into the branch pipes and push the sewer gas through the traps (the bubbling sound) and out into the house. The smell would appear in every room that had a drain in it.