Pressure and temperature control valves regulate pressure and temperature in steam and liquid applications. Air and vacuum release valves have an air release valve and an air vacuum valve in a compact unit. Boiler feed valves maintain water pressure by filling boilers and piping systems with water. Mixing valves blend cold and hot water in hot water supply systems. Gas pressure regulators reduce the pressure of gas supplied from a high-pressure cylinder of gas to a safe, workable level. Pressure-reducing automatic control valves reduce a fluctuating higher upstream pressure to a constant lower downstream pressure regardless of varying flow rates. Single use rupture discs provide rapid pressure relief to protect equipment or a system. Water hammer arrestors control water pressure shock and silence water pipe noise caused by the sudden closing of a valve in a pipeline.