Why you should not leave your grey valve open - Sewer Rats

Rats coming up the sewer lines into a toilet and out into your house? Happens a lot. Think about it. Your sewer line or, in this case, your sewer hose usually has no water flow unless it's used to drain material like waste from a sink or waste from the toilet. Well if the dump valve is left open, a rat has absolutely no problem getting up the hose and into the black water tank. How it would get past the flapper valve thing in the toilet is another thing. Hopefully it doesn't happen when the toilet is in use and the valve is opened. In houses the rat only has to swim down and up through the p trap that's built into the toilet. Rats are excellent swimmers and often enter homes through broken sewer lines or through clean outs when the covers are left off.