INDESTRUCT FREEZE PROOF WATER COOLERS are rated for industrial duty. They are built with the most durable materials and components to withstand even the most demanding outdoor environments. Heating elements are used on key internal components to prevent freezing. Heavy stainless steel tank tested at 250 psi for 125 psi working pressure with heavy stainless steel immersion coil type evaporator. Tank storage equal to at least 1/2 of recovery capacity to meet all peak demands for drinking and thermos filling at breaks, shift changes, etc. Insulated tank housed in a rust-proofed steel box.