Hot water temperature fluctuates between hot and cold during use, especially at low flow rates.

Safety: Water may suddenly become very hot; take care when testing taps or showers.

• Test at different taps: Check if the issue occurs at all hot outlets or only one, to rule out local mixer valve problems.
• Increase flow rate: Run the tap fully open. Many combi boilers, including Biasi, regulate better at higher flow rates.
• Clean inlet filters: Ensure the cold inlet filter and any strainers are clean to maintain stable flow.
• Engineer checks: A technician can test the DHW NTC, descale or replace the plate heat exchanger, and verify gas valve modulation and combustion settings.