State
Flow Restriction / Partially Closed Valve
State water heater: whistling or high-pitched noise occurs when hot water is running.
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Possible Causes
Partially closed shutoff valve, Debris in the inlet or outlet, Partially clogged mixing valve, Scaled heat exchanger (tankless)
How to Fix / Troubleshooting
Safety: Use caution around hot piping.
- Check valves: Ensure the cold inlet and hot outlet shutoff valves are fully open.
- Clean aerators: Remove and clean faucet aerators and showerheads.
- Inspect mixing valve: If installed, service or replace a noisy thermostatic mixing valve.
- Tankless descale: For tankless models, perform a descaling flush of the heat exchanger.
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Repair Difficulty
Easy
2/5
Required Part
Inlet Shutoff Valve or Mixing Valve
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