Return to FAQs

Water Hammer Arresters Frequently Asked Questions

  1. Will water hammer arresters control the movement in piping mains?
    The movement in piping mains is caused by shock and partially by the flow of water through the mains. The greatest movement is caused by shock which can be controlled by the installation of water hammer arresters. The movement caused by water flow can be controlled by the proper placement of pipe hangers and supports.

  2. Is it possible to control the shock created by pumping equipment?
    When a pump shuts off, some degree of shock will be experienced in the discharge line. This is caused by the back surge of water to the pumping equipment. The shock can be controlled in most applications by the installations of a properly sized water hammer arrester. The unit should be installed at a tee connection in the vertical discharge line.

  3. Will a water hammer arrester prevent check valve slam?
    A  water hammer arrester will absorb the shock and minimize the slam noise. A soft seat in the check valve will then assure a quiet closure.

  4. Is the shock generated in dishwasher piping controllable?
    A solenoid or other type of quick closure valve is employed for dishwasher applications. A properly sized water hammer arrester installed on the pressure side of the solenoid valve will eliminate the shock and noise.

  5. Is the shock generated in home washing machines controllable?
    Yes, a properly sized water hammer arrester placed on the cold and hot water supplies to the washing machine will absorb the shock as caused by quick closure devices.

  6. Can shock be prevented in other types of liquid conveying systems?
    The 5005-5050 stainless steel bellows units can be used with most types of liquid conveyed in a piping distribution system. Therefore, if a shock is encountered, it can be controlled. When liquids other than water are involved, it is recommended that Smith’s Sales Engineering group be consulted for evaluation.

  7. Will water hammer arresters eliminate piping vibration?
    If the vibration is caused by the occurrence of shock in the piping system it can be avoided if a properly sized water hammer arrester is installed near the quick closure valve.

  8. Are water hammer arresters required in the average residence?
    Yes, a severe shock can occur in the residential piping system, especially when excessive water pressures are involved. Most of the premature failures of piping, hot water storage heaters, home laundry machines, automatic control valves and flush tanks or valves, may be attributed to shock caused by quick closure valves. Properly sized water hammer arresters should be installed on the hot and cold water supply piping to that fixture, equipment or apparatus wherein shock can be produced. A pressure reducing valve installed on the discharge side of the water meter can be most helpful in protecting the residential piping system.

  9. Do Water Hammer Arresters require access panels?
    It is always wise to provide access to any mechanical device that may need servicing or replacing during the life of the building. 

  10. Can a Water Hammer Arrester be placed at the top of a riser and be effective?
    No. The location of the unit itself is essential for proper operation and effectiveness. Usually, the top of the riser is so remote to the source of the problem, the unit never has an opportunity to perform its job. The location should be at the piping serving the fixture(s) and normally between the last two fixtures. Refer to the Smith ‘Yellow Pages’ catalog, Water Hammer Arrester section for complete information on sizing, placement and selection. The Plumbing & Drainage Institute (PDI) Water Hammer Arrester Standard, WH-201, may also be referred to for sizing, placement and selection.

  11. Where are water hammer arresters required?
    Water hammer arresters are intended for use in either cold or hot water supply lines. Generally, they are needed anywhere quick closing valves are installed. Such valves can come in the form of faucets, flush valves, washing machines, dishwashers, etc. Jay R. Smith Mfg. Co.’s water hammer arresters are available in multiple types, connection sizes and capacities for various applications. Each version is designed to control the destructive shock of water hammer when these quick closing valves are operated. The internal construction of these devices allow them to absorb and reduce intense pressure spikes, which occur in these instances, to safe levels, preserving the piping system. The sizes and locations are typically specified by the plumbing engineer of record for a given facility. In order for water hammer arresters to work as designed, they must be sized correctly based on the number of fixtures and located properly in the water piping system to effectively mitigate the damaging force of water hammer.