If your boiler keeps losing pressure, topping it up may restore heating temporarily, but it does not explain why the pressure is dropping.

For homeowners in Denham, recurring pressure loss is a reason to arrange an assessment. The problem could be within the boiler or elsewhere in the heating system, and it does not automatically mean you need a replacement.

Why Is My Boiler Losing Pressure?

1. A Leak in the Heating System

Water escaping from radiator valves, pipework or connections can cause the pressure to fall. Some leaks are easy to spot, while others may be hidden beneath floors or behind walls.

Look for visible damp patches, staining or water around accessible radiator connections. Make a note of anything you find so you can show your engineer.

2. A Fault Inside the Boiler

Pressure loss can also result from a fault within the appliance. An engineer may need to inspect internal components to establish the cause.

Do not remove the boiler casing or attempt internal repairs. Record the boiler make, model and any fault code before arranging a visit.

3. An Expansion Vessel Problem

The expansion vessel helps accommodate changes in water volume as the heating system warms up. If it is not working correctly, the pressure may rise excessively while the heating runs and then fall after the system cools.

Tell your engineer if you notice a large difference between the pressure when the system is cold and when it is hot.

4. Water Escaping Through the Pressure Relief Valve

The pressure relief valve releases water when system pressure becomes too high. If the valve continues to let water escape, the boiler may subsequently lose pressure.

An engineer can investigate both the valve and the reason for any excessive pressure. Do not block or interfere with discharge pipework.

5. Recent Radiator Bleeding or Heating Work

Pressure can drop after radiators have been bled or water has been drained during maintenance.

A one-off change following this work is different from pressure that repeatedly falls. If it continues dropping after the system has been correctly refilled, arrange an inspection.

What Pressure Should My Boiler Be?

The correct pressure depends on your boiler and heating system. Check the manufacturer’s user manual for the recommended range and whether the reading should be taken with the system cold.

Avoid relying on a single pressure figure for every boiler. If the reading is outside the recommended range, follow the manufacturer’s guidance or contact a heating engineer.

Can I Repressurise My Boiler Myself?

Some boilers have a filling arrangement intended for homeowner use. Only follow the instructions for your specific model if you can clearly identify the correct controls and understand the procedure.

If you are unsure, cannot find the instructions or the pressure keeps dropping after refilling, contact an engineer. Repeatedly adding water should not become a substitute for finding the fault.

When Should You Call a Heating Engineer?

Arrange an assessment if:

• The pressure repeatedly falls after topping