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Water Hammer on System Start/Stop—Broken Head and Pressure Regulator

1997 home, recent water hammer on system start AND stop. Plumber installed arrestor after shutoff — no help. Broken head (water spilling), some heads malfunctioning.

Root Cause

Broken head = massive flow increase → worse water hammer. More water volume = bigger shock wave.

Fixes

Replace broken head FIRST — reduces flow volume significantly
Pressure regulator on mainline (before/after vacuum breaker) — reduces flow velocity
Verify system design pressure after regulator still adequate for heads

Why Arrestor Didn't Work

Installed after shutoff — may be too far from hammer source. Fix flow volume first.

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