Drain snake - Can I charge everybody

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I have a 7 unit with two commercial spaces. There was a complaint that there was a backup and I had it snaked a couple of times and the plumber found rags. I sent out a notice to all of the tenants not to flush paper towels, rags, feminine products and that sort. Fast forward 4 months and it looks like it happened again. I'm not able to determine who is the culprit in putting items down the drain. It's very costly to get someone to come out and snake the system. Is there any way I can get everybody to pay the bill or what have people done in their experience? Thanks