How Rats Enter Homes Via Sewer Pipes
Rats coming up sewer pipes is a serious issue and in many cases can be nearly impossible to solve. The best and many times only solution is to call a leak detection company and have them perform a smoke test.
The the Clearwater area of Florida, we are seeing this problem more and more with rats. In many (but not all) cases, we have a feeling this is an issue when we do an inspection. However, you must eliminate all potential openings before coming to the conclusion that rats are entering through the sewer. The exception being when you are lucky enough to find the sewer pipe being used. It will be obvious as rats using the pipe will result in brown staining on the pipe.
This is frustrating for all parties because the the pest control companies must go through ALL the steps, a process of elimination, monitoring all the typical openings around the building. When it is determined there are no typical openings being used, the logical conclusion is that a sewer pipe is being used and must be found in order to solve the issue long term.