Boiler runs but domestic hot water is insufficient or fluctuates (on Utica combi or with indirect tank)

Safety first: Hot water can scald. Use caution when testing taps.

• Check DHW temperature setting: Verify the domestic hot water setpoint on the Utica control or mixing valve is appropriate (typically 120°F/49°C).
• Clean faucet aerators: Remove and clean aerators and showerheads that may be restricting flow.
• Inspect mixing valve: If a thermostatic mixing valve is installed, ensure it is not stuck or set too low. Exercise the valve by turning through its range.
• Plate heat exchanger: On combi models, a scaled plate heat exchanger can reduce output. Descaling should be done by a professional using appropriate chemicals.