Hpt Spring MPS 5lbs Part Number: 71532 For clear and sparkling hot tub water, treat your tub! Watkins Freshwater MPS Shock will leave your water clear, odor-free and fresh. If you frequently use your Hot Springs Hot Tub, it is recommended that you shock your spa at least once a week - or for every hour of use, whichever is greater. You can do this by using Watkin Freshwater MPS Spa Shock. Freshwater Hot Springs MPS is a non-chlorine spa shock (oxidizer) used to effectively reduce odor-causing ammonia and chloramines as well and soaps and oils. Hot Spring Spa Supplies carries spa fragrances, air & water valves, control systems, filter accessories, lights, cleaners, pumps, thermostats, and more for virtually every hot spring model.