Older homes often have pipe fittings known as air chambers, which are rarely visible and located on each hot and cold water line near each faucet or water inlet valve. These air chambers act as a shock absorber for water flowing at high speed. A plumbing bladder is a device manufactured by a plumber, which is simply a piece of pipe attached to the water supply lines between the shut-off valve and a faucet, spigot, or any plumbing outlet. Ready-to-use plumbing air chambers are also available.
Most air chambers are installed vertically on horizontal supply lines. If the supply line is already in the vertical position, an additional length of short horizontal pipe can be added. This dead-end pipe partially intersects the water flow, creating an air pocket. Water hammer, also known as hydraulic shock, is a concussion sound caused by moving water against the sides of a pipe or container.
To solve this problem, a water hammer suppressor or an air chamber may be required. An air chamber is an extension of the water supply pipe near the pipe fitting that provides an air cushion to absorb hydraulic shock. If you look at the image below, the pink lines you see are the actual “air chambers”, while the other lines are the hot and cold water supply, and the drain and vent pipes. The most common cause of a water hammer is an air chamber (or several air chambers) with too much water in it.
Air chambers are vertical pipes that regulate pressure and prevent water from forming waves in the supply pipes. If you don't have them, ask a professional to install them at key points in your system to eliminate the waves that cause water hammers. Many homes have air chambers installed inside their walls, but sometimes they can stop working properly if they get soaked in water.