PiS would soon lose votes.
Perhaps not, because PiS don't actually control that many local governments. It would probably hurt wealthier gminas more, because they're the ones likely to have nice things like swimming pools to pay for. A poor rural gmina would only really have to fund schools and not much else, and even then, they'd get away with only funding primary schools. Those poor gminas could also be subsidised in some way by central government, while forcing those in wealthier areas to pay more.