Regal 29-60121-90 900mL Stain Protect naturally prevents staining and water colouration from metals in spa water. Used on a regular basis, it also prevents corrosion of the spa equipment. In addition, STAIN PROTECT eliminates and prevents scale build-up on spa surfaces. Spa can be used immediately after the addition of STAIN PROTECT. Its natural and biodegradable formula also makes it safe for the environment and does not add phosphates to the water.