That was one of the things my cousin said when we visited a couple of weeks ago (North West Scotland). 'Oh by the way, no wipes down the loo, only toilet paper as we are on a septic tank'.
Our rule was that you first had to eat whatever you put down the toilet.
Then we had gormless tenants whilst we were abroad for a tour.
3 months in I get a fax from them "the toilets broken and the council laughed when we phoned them"
I replied " It's a septic tank, everyone in the village has one, it's in the lease and the instructions. I'll send the agent round and he'll explain"
He did this and made them pay for the clean out and revitalise that was necessary.
They were very pissed about this. But he showed them the bit in the lease and the instructions book that explained about the septic tank and how it should get cared for.
He requested one of them be present to witness that the rank had been emptied and they had not been scammed.