So we all know that Rodents are known for biting and gnawing, in fact "rodent" comes from ancient Greek which literally means "to gnaw". Now gnawing is a characteristic of all rodents... but just how hard can they bite?  The average rat has a bite force of up to 6000 psi and grey squirrels reaching 7000 psi. To put this in comparison, a human has a bite force of 160psi, which is astonishing when you compare the size difference. So in a nut shell, if a rat wants to chew through your steel drain pipe, then that's exactly what its going to do.