Scale Inline Crtdge W/Brs Ftng For outdoor use only, do not install indoors. Not for potable water. Controls scale buildup and corrosion in coolers. Special formula holds minerals in suspension by raising the solubility level of the water. Reduces mineral buildup on pads and must be us ed with a bleed off kit or "PowerClean" purge pump to flush suspended minerals. Lasts up to 3 months and is easy to install.