Why is my boiler losing pressure?

A small water leak in the system is the most common cause. Check for puddles under radiators, pipe joints, and around the boiler itself.

When you bleed radiators to release trapped air, you remove water from the system, which lowers pressure. Repressurize the system after bleeding.

A faulty expansion vessel can't properly accommodate water expansion as it heats, causing pressure fluctuations. This requires professional replacement.