Keeping Water in My Freshwater Tank During Storage?

I drain mine in storage, but I own the building where its stored. When ready to hit the road, I add about 1/3 tank, but I don't treat it. I only use it for the toilet and the shower and only while in transit. I always stay at FHU CGs and hook up to water then. For cooking, drinking and soaking my teeth, I buy gallon jugs of distilled water all the time. The outside of me is waterproof.