Sioux Chief 660-GTR piston-type water hammer arresters shall be installed where required on supply valves. Water hammer arresters shall be specifically sized and have sufficient volume of air to dissipate the calculated kinetic energy generated by closing residential or commercial faucets or valves. Arresters shall be installed on both hot and cold lines on the supply stops where applicable. Arresters shall be approved for installation with no access panel required. Water hammer occurs when the flow of moving water is suddenly stopped by a closing valve. If no measures are taken to control it, expensive fixtures and appliances within the plumbing system may become damaged. This can lead to fractured pipe joints, leaking valves, burst laundry hoses, and premature failure of water heaters and other appliances.