Excessive use of washer by tenant

[Tiffany Tan]

I have a duplex, I live in one of the units and rent out the other one. Both units have washer/dryer, and the water bill is under my name.

My tenants (a couple) are good, they keep my unit nice and clean, not much noise, and they would pay rent after being reminded. But since they move in my water bill is doubled. And during the weekend when I am home, I know that the girl would do at least 6 loads per day, they guy normally does 2 loads on top of that. And I don't know how many loads they do during weekdays when I am not home.

I don't know how to prove if this is an excessive use of washer, but I wonder if it's acceptable to remove the washer or replace the washer to a coin-operated washer (uncommon in Philly) upon lease renewal?

Alternatively, I could share the water bill with them but I am not confident it would work since I need to remind them about the rent each month already

Please help! Thanks!