Boiler displays A13, often associated with low system pressure or recent draining

Safety: Do not overfill the system. Overpressure can cause relief valve discharge and damage.

• Check pressure gauge: If below the recommended level (typically 1.0–1.5 bar cold), top up using the filling loop as per the De Dietrich manual.
• Bleed and recheck: After topping up, bleed radiators and recheck pressure. Repeat until stable.
• Inspect for leaks: Look for visible leaks at radiators, valves, and under the boiler. Fix any leaks before topping up again.
• Technician tasks: If pressure drops repeatedly, a professional should test the expansion vessel charge, check the pressure sensor, and inspect for hidden leaks.