Designed specifically to sanitize hard non-porous surfaces of water holding tanks in RVs, trailers, campers and boats. The first and only sanitizer specifically for the entire fresh water plumbing system of RVs and boats. The best times to use it are to start the season and after the vehicle sits for any length of time. Can also be used on remote tanks, water coolers and hoses. Chlorine free formula is EPA registered in all 50 states.