I pretty much do the same thing as Horned Toad. We always leave a bit of water in the tank for potty stops coming and going. Drain it down at the end of the year, unless there is an issue. FWIW we are using chlorinated city water in ours. We don't use it for cooking or drinking, just flushing, showers and washing up.
Maybe check around and see if your drain down valve could be moved somewhere that would be easier for you to reach? Mine is just under the front edge of the trailer and easy to get to, and mine is an actual valve not a pipe and plug fitting like some I have seen.
Aaron