Journeyman Plumber ExamFixtures, Faucets, and Other AppliancesMedium
A plumber is installing a water-hammer arrestor on a washing machine supply line. Which of the following statements best describes the principle by which a water-hammer arrestor functions?
- AIt provides an air or gas-filled cushion to absorb pressure surges.
- BIt constricts water flow to reduce pressure fluctuations.
- CIt uses a spring-loaded valve to slowly close off water supply.
- DIt diverts excess water directly into the drainage system.
Show answer & explanationAnswer & explanation
Correct answer: A. It provides an air or gas-filled cushion to absorb pressure surges.
Water hammer arrestors typically contain an air or gas-filled chamber separated by a diaphragm or piston. When a valve suddenly closes, the pressure wave from the water hammer compresses the air/gas, absorbing the shock and preventing noise and pipe damage.
Why the other options are wrong
- B. Constricting flow would reduce the effect but might also limit appliance performance; it's not the primary mechanism.
- C. This describes a slow-closing valve, which prevents water hammer but is not how an arrestor itself functions to mitigate existing hammer.
- D. Diverting water to the drain would be wasteful and is not the function of a water hammer arrestor; it addresses the pressure surge in the supply line.
Water Hammer Arrestor Principle
A device designed to prevent water hammer by absorbing the shock waves generated by the sudden closure of a valve in a plumbing system.
- Contains an air or gas-filled chamber.
- Uses a diaphragm or piston to separate water from the compressible medium.
- Absorbs pressure surges, protecting pipes and fixtures.
Memory trick: An arrestor is like a 'shock absorber' for your pipes.