First, I'm not sure that this is what's happening but I suspect this is the problem. On occasion my wife and I find cockroaches in our house. This isn't very frequent (I'll find one once every few months) and we also have an exterminator who comes and sprays once every month.
However these random cockroaches tend to always be found near or in our bathrooms and, to my recollection, we've never found one in our kitchen or dining room – places where vermin could most certainly find food.
I've heard that if you lose water on your sewer line, vermin can come in through the sewers. Is this true? If so, what can I do about it? I also suspect that this may be happening because there have been a few cases where on the back end of our house (near a spare bathroom that is infrequently used) we will get a sewage smell. The smell is quite rare, and we've checked for leaks around the toilet, yet we can't find any problem with the toilet itself.
Are we losing pressure on the sewage line, which is suctioning the water from the toilet bowl and allowing vermin into our home?
If this is the case, this is super-nasty. Please advise.
Best Answer
The smell of sewage is definitely a bad sign and means that either a trap has gone dry or a connection somewhere is bad releasing sewer gasses. Maybe this is related to the vermin, maybe not, but its definitely something that needs a resolution.
When checking traps, check:
Are all your toilets full of water?
Do you have any sinks or fixtures that are very infrequently used (eg: basement laundry sink)?
Do you have drain and trap in your basement floor? Does it have water in it? Is there a trap primer hooked up to it (this is a small pipe that is connected to a frequently used fixtured so that when you run the fixture, a small amount of water flows into the trap and keeps it full)
Other things to check:
Do you have a sewer clean-out inside your house? If so, is the cap done up tightly? Also check the gasket on it - they can dry up and start leaking sewer gasses due to the poor seal.
Bottom of toilets - flush each one a couple times and look for small amounts of water near the base. This would indicate a failed wax ring. Make sure to flush a number of times because if the leak is very small, it might not be noticable after a single flush.
Vents on roof - are any drain vents near air intakes (sucking the sewer gasses back in to your house)
Signs of a sewer line blockage - gurgling sinks, slow draining fixtures, sewage coming out of the lowest drain in your house (often the floor drain in your lowest level)
I had a situation in my house where one of the connections in the clay sewer had sunk by an inch or so. This would cause stuff like toilet paper to start collecting resulting in a partial blockage. Overtime, it would get more blocked until finally the pressure of the water combined with atmospheric pressure would cause it to push through. During this process, it would suck all of the water out of my basement floor trap and I'd go from a full trap to a completely empty trap very suddenly. Another interesting thing here was that when running a camera through my sewer, I noticed spider webs in them, so that definitely seems to indicate that some critters might come up from the actual sewer itself.
Ultimately my point here is that it can be a lot of things and if you can't find the cause on your own it is advisable to call a plumber - the sewer gasses are not something you want to be breathing in all day.