Boiler displays A04, no heating or hot water, pressure gauge near zero or flashing low-pressure symbol.

Safety: Ensure the boiler is cool before topping up. Do not over-pressurise the system. If pressure drops repeatedly, there is likely a leak that must be found and repaired.

• Check pressure gauge: Note the current reading. For most Beretta boilers, 1.0–1.5 bar when cold is recommended.
• Top up via filling loop: Locate the filling loop (flexible hose or built-in valves). Open the valves slowly until the gauge reaches about 1.2 bar, then close both valves firmly.
• Bleed radiators: After topping up, bleed radiators starting from the highest. Re-check pressure and top up again if needed.
• Inspect for visible leaks: Look around radiators, valves, and under the boiler for signs of water. Check the discharge pipe outside (pressure relief valve outlet) for dripping.
• Expansion vessel check (technician): With system pressure at zero and drained if necessary, measure the expansion vessel air charge. Re-pressurise or replace the Beretta expansion vessel if the diaphragm has failed.
• If pressure keeps dropping: Contact a heating engineer to locate hidden leaks or internal boiler leaks (e.g., in the plate heat exchanger).