Check the manufacturer’s guidance
Read the pressure gauge and the instructions for your exact boiler model. Many sealed heating systems have a recommended cold pressure around 1–1.5 bar, but the correct range and filling procedure depend on the appliance and system.
Look for visible signs of a leak
Check accessible radiator valves and visible pipework for dampness without removing the boiler casing. If water is near electrical parts, keep clear and get professional help. Pressure loss can have several causes; a hidden leak is one possibility.
Has the system recently been worked on?
Bleeding radiators or carrying out repairs can reduce system pressure. If the pressure changes repeatedly, record when it happens and any fault code so an engineer has useful information.
A component may need attention
An expansion vessel, pressure relief valve or another component can cause pressure problems. Internal boiler inspections and repairs need a suitably qualified engineer.
Before you top it up
Use only the filling procedure in the manufacturer’s instructions for your boiler. Some use a filling loop; others use a key or a different mechanism. Do not open unidentified valves, exceed the recommended pressure or repeatedly refill a system with an unresolved fault. If you are unsure, call an engineer.
When to call us
Call if the pressure keeps dropping, you can see a leak, the gauge rises excessively or the boiler shows a fault code. Tell us the make, model and symptoms. Call 07719 522450 or send a photo on WhatsApp.