Soft Soak Trio Spa Kit is a simple spa water system that requires no measuring for spa with 350-450 gallons of water. Step one is added at start up and uses minerals and salts to enhance the feel of the water. Step 2 is added weekly, it removes water impurities, prevents scaling and corrosion and replenishes the softness of your water. The last step is before draining the tub as it breaks down oils, grime, lotions etc on the spa surface and plumbing.