Water heater frequently loses pressure on the primary (heating) side, requiring regular top-ups

Safety: Allow the system to cool before depressurizing or checking the expansion vessel.

• Check relief valve outlet: Look for signs of water discharge at the relief valve pipe termination.
• Inspect expansion vessel: With system pressure at zero, measure the air charge. Recharge or replace if the diaphragm has failed.
• Look for leaks: Inspect all visible pipework, radiators, and joints for damp patches or staining.
• Monitor pressure: After topping up, monitor pressure over several days. Persistent loss indicates a leak that should be located and repaired by a heating professional.