How long to keep potable water in holding tank

Hi folks.

We will be camping four weeks from now at an electric-only campground (no water hookup). The water quality is questionable where the trailer will be stored until then so I filled the holding tank today with good water while I had that option. How long will a full tank of water remain safe to drink sitting still? Was this a bad idea? And should I drain the hot water tank in the meantime? (it is currently full from camping this week). I have heard that it can get stinky.

Thanks.