distilled water is a good practice. I don't bother myself I bought the extended warrantee for 3 years. I run mine 24/7 at a medium rate and it keeps the room (full sized unit here) at 54-66% so I have no complaints so far it has been almost a year now. I have 8 no make that 9 snakes so it is more efficient for me to use a large one but the principal is the same.