This standard applies only to those devices classified as water hammer arresters having a permanently sealed cushion of water or gas isolated from the waterway, and designed to provide continuous protection, without maintenance, against detrimental surge pressures within the water distribution system. Water hammer arresters are installed on water distribution system piping to prevent over pressures within water distribution systems, thereby prolonging the service life of valves, piping, fittings, trim, equipment, appliances, appurtenances, and other devices which are part of the distribution system; and to eliminate noise.