Plumbing valves control the flow of water, gas, and other fluids in plumbing systems. Flow control valves regulate fluid pressure and flow rate. Pressure control valves and temperature control valves regulate pressure and temperature in lines. Check valves and backflow preventer valves help protect potable water supplies from contamination due to the reverse flow of polluted water in pipes and fixtures. Float valves automatically open or close when a liquid reaches a predetermined level. They can be used to control filling or drainage in open or closed tanks, storage tanks, cooling towers, and reservoirs. Solenoid valves can actuate either a pneumatic or hydraulic valve to shut off, release, distribute, or mix fluid in a variety of applications.