Autofilling Humi for Walk In

You don't necessarily need a distiller. Most cities have at least 1 water store that provides distilled water. Depending where you get it, you can probably find it for around 50 cents per gallon. $2.50 could stock you for maybe up to a month. If you go the 5-gallon route you could probably even set up a gravity feed system. No need to worry about pumps failing or anything.