Thoroughly cleans the plumbing system purging the organic build-up. Restores spa plumbing to its original condition! Directions for Use: 24 hours before a planned drain & refill remove cartridge filter elements and soak in Natural Chemistry's Filter Perfect. Do not reinstall filter elements until Spa Purge process is complete. With spa water temperature at 95deg;F or higher, circulation pump running and jets off, add entire contents of 1L Spa Purge bottle to spa water. After 20 minutes, run jets of a minimum of frac12; hour. The next day, drain, rinse and then refill spa and reinstall filter elements. Proceed with normal spa maintenance.