Despite John's detailed technical explanation, ALL TP in my house is, and will continue to be, mounted so that it exits from the top/front of the roll. It is simple to unroll the desired length, then place the fingers on the top of the roll and tear off at the desired perforation while holding the next sheet firmly in place.

If the dispenser is mounted so as to become damp from splashes, THAT needs to be changed. I can't say I have EVER had that problem..(and I even lived in Kansas for 35 years! *grin*)