Why Does My Boiler Keep Losing Pressure?

Keeping your boiler functioning optimally is essential, particularly during colder months when a reliable heating system is crucial. One common issue many homeowners face is a boiler that continually loses pressure. When boiler pressure drops, it can lead to inadequate heating, lack of hot water, and potential damage to the system. In this guide, we'll explore the common causes behind pressure drops, steps for diagnosis, and preventive measures to keep your boiler running smoothly.

Understanding Boiler Pressure

Boiler pressure is a measure of the pressure inside the heating system. For most modern boilers, this should ideally range between 1.0 and 1.5 bars when the boiler is off. When heating up, the pressure may rise slightly but should not exceed the green zone (often up to 2 bars). Consistently low pressure or pressure that rapidly fluctuates indicates a problem that needs attention.

Why Does Boiler Pressure Matter?

Proper boiler pressure is essential for efficient heating. When pressure drops too low, the system won't function correctly, affecting both central heating and hot water supply. Moreover, frequent or rapid drops in pressure may suggest a more severe issue, such as a leak or a malfunctioning internal component.

Common Reasons Your Boiler Keeps Losing Pressure

1. Recent Radiator Bleeding
Bleeding a radiator releases trapped air, which helps maintain even heating across your system. However, the process also causes a drop in water pressure within the system, resulting in lower boiler pressure. If you recently bled your radiators, check your boiler's pressure gauge. You may need to top up the system pressure by opening the filling loop.

2. Leaks in the Heating System
Leaks are a common culprit behind pressure drops. They can occur anywhere in the system, particularly at joints, connections, or the radiators themselves. Look out for signs like damp patches, rust, discoloration on pipes, or pooling water around fittings.

3. Internal Boiler Leaks
If there are no visible leaks in the pipework or radiators, the leak may be internal within the boiler unit itself. Common causes include:

• Corroded or loosened components
• Faulty Pressure Release Valve (PRV)
• Damaged Expansion Vessel

How to Repressurise Your Boiler

Follow these steps to repressurise your boiler:

1. Turn off the boiler and allow it to cool down
2. Locate the filling loop (usually a flexible hose beneath the boiler)
3. Open the valves slowly and monitor the pressure gauge
4. Close the valves once pressure reaches 1.5 bars
5. Monitor the pressure over the next few days

Preventing Future Pressure Drops

To maintain consistent boiler pressure and reduce the risk of future issues:

• Schedule annual boiler services with a Gas Safe engineer
• Check pressure regularly, especially during winter
• Bleed radiators correctly and monitor pressure afterward
• Inspect pipework and radiators for signs of leaks

Frequently Asked Questions

How Often Should I Repressurise My Boiler?
For most homes, repressurising once or twice a year is normal, particularly after bleeding radiators. More frequent drops may indicate an underlying issue.

Is Low Boiler Pressure Dangerous?
While not typically hazardous, low pressure can disrupt heating and hot water supply. Prolonged low pressure may lead to component wear and should be addressed promptly.

If you're experiencing persistent pressure issues or need professional assistance, don't hesitate to contact Home Heating Services. Our experienced team of Gas Safe engineers can diagnose and resolve your boiler pressure problems efficiently.