How do you charge tenants for repairs?

[Lana LeMay]

I am  trying to crack down on charging tenants for damages they cause (or allow). I have two primary questions:

1) Do most of you charge actual expenses, or do you have a chart that lists common damages with an expense attached? If you charge actual expenses, how do you determine the expense if multiple repairs were made (as in a vacancy) and some were not tenant related?

2) How do you prove they caused the problem when it's not straightforward? Ex: We have a duplex where the kitchen drains are tied together. We've had a backup due to grease more than once. Both tenants deny it, but we "know" where it's coming from. Also, I handle a small, 18 unit apartment complex where some drains are tied together. We can assume the smokers are putting the cigarette butts in the drains and the wipes are coming from the parents, but people always want to argue that you can't prove any of that.