I have seen plastic piping of all kinds (PEX, PVC irrigation pipe, ABS and PVC DWV) severely rat-chewed. I drive a van whose steering wheel
has many gnaw marks on it. Rodents are terrible, terrible creatures.
Even worse when they chew up your romolex. Had a panel stripped bare - and the sucker lived. "finalblox" is the key - one feed and they are gone - smells so good I could eat it. gophers and rats like it too