PVC true union ball check valves are used in systems that allow water to flow in one direction and also prevent backflow in the line. Ball check valves are equipped with a cone or round ball inside the valve that checks up in the valve when a system is turned off to prevent the backflow to the system. The union ends on the valves allow for maintenance of the valve itself, O-rings, and seals. Repair or replacements are very easy processes with these check valves because of the union ends. No need to cut an existing line to work on the system when you use these valves. These valves are made from sturdy gray PVC material and are made to withstand pressures suited for PVC materials. PVC check valves guard against corrosion, wear, rust and is compatible to many chemicals. PVC true union ball check valves are designed to handle a max temperature of 140 degrees F.