Domestic hot water temperature fluctuates, alternating between hot and cold

Safety: Hot water can cause scalding. Use caution when testing taps.

• Step 1 – Check flow rate: Ensure a steady flow at the hot water tap. Very low flow can cause cycling. Clean faucet aerators and showerheads.
• Step 2 – Inspect DHW filter: On Triangle Tube combi models, clean the cold water inlet filter screen to restore proper flow.
• Step 3 – Mixing valve: If an external thermostatic mixing valve is installed, verify it is not stuck or set too low. Exercise the valve by turning through its range.
• Step 4 – Professional descaling: A technician should flush the plate heat exchanger and DHW circuit with descaling solution if scale buildup is suspected.