Our pool created a rule this summer that no kid (aged 4 and under) can be in the main swimming pool, period. This includes with a parent and regardless of whether or not they are wearing swim diapers. They are only allowed to swim in the baby pool, full stop. You can imagine the controversy this has caused.
I find this to be a ridiculous rule and plan to fight it, but was wondering whether it is more pervasive than I thought. The rationale seems to be related to keeping poop/vomit out of the pool but traditionally, this has not been a problem for this pool and when it has been, it's not exclusively a 4 and under problem! Seems like a sledgehammer to an ant, IMHO.