Y adapter for fresh water at park water supply post?

No, been doing it for years and we're still alive to talk about it. If you are really concerned get the one with the cutoffs on each end of the Y fitting. That way when you leave the RV, if you want to shut the water off to the RV while you are away for the day, it's easy to do so. And when flushing, you can also shut off the fresh supply if you feel the need to.