To get the pressure back in your boiler, you typically need to repressurize the system by introducing more water into the heating circuit. The most common method involves using the boiler's filling loop, which connects your domestic cold water supply to the central heating system.
Boiler pressure often drops over time due to minor leaks, bleeding radiators, or system maintenance. Maintaining the correct pressure is crucial for your boiler to operate efficiently and safely.
Understanding Boiler Pressure
Most domestic boilers operate optimally when their pressure gauge reads between 1 and 1.5 bar when the system is cold. If your boiler's pressure drops significantly below 1 bar, it may stop working, display an error code, or shut down as a safety measure. Always consult your boiler's manual to confirm the recommended pressure for your specific model.
Repressurizing Your Boiler: The Filling Loop Method
There are two main types of filling loops: external and internal. The process is similar for both, but the location of the taps or valves differs. The provided reference describes an external filling loop.
1. Using an External Filling Loop
An external filling loop is a separate flexible hose that connects your mains cold water supply to your central heating system.
Here's how to use it:
- Locate the filling loop: This is usually a braided or flexible hose that connects two pipework points near the bottom of your boiler or a nearby pipe. It will have two small taps or valves, one at each end of the hose.
- Attach the hose (if not already connected): Ensure the flexible hose is securely attached to both sides of the valve or the designated connection points.
- Open the mains cold water tap: Turn the first tap on the filling loop, which is connected to your cold water mains, fully open. You might hear water beginning to flow.
- Open the second tap: Slowly open the second tap on the filling loop. This tap allows the mains water into the heating system. You should hear water entering the boiler and pipes.
- Monitor the pressure gauge: Keep a close eye on your boiler's pressure gauge. It will typically be on the front panel of your boiler.
- Stop when pressure reaches just about 1 bar: As the pressure rises, turn off both taps on the filling loop as soon as the needle reaches just above 1 bar. It's better to slightly under-pressurize than over-pressurize.
- Close both taps securely: Ensure both taps are fully closed to prevent over-pressurization or backflow into the mains water supply.
- Detach the hose (for external loops): If you have an external filling loop, it's good practice to detach the hose after use to prevent accidental repressurization or cross-contamination. Ensure no water leaks out when disconnecting.
2. Using an Internal Filling Loop
Some modern boilers have an internal filling loop, which means the connection and valves are built directly into the boiler's pipework, often discreetly located underneath.
The general steps are similar:
- Locate the internal filling valves (often small levers or knobs).
- Slowly open them to allow water into the system.
- Monitor the pressure gauge.
- Close the valves securely once the pressure reaches the desired level (typically 1 to 1.5 bar when cold).
What if the Pressure Keeps Dropping?
If you find yourself needing to repressurize your boiler frequently (more than once every few months), it indicates an underlying issue. Common reasons for persistent pressure loss include:
- Leaks in the system: Even small leaks from pipes, radiators, or boiler components can lead to a gradual pressure drop. Check for visible signs of water.
- Faulty pressure relief valve (PRV): This valve is designed to release pressure if it gets too high. If it's faulty, it might be constantly dripping or releasing water, causing pressure loss.
- Expansion vessel issues: The expansion vessel absorbs excess water pressure as the system heats up. If it's under-pressurized or faulty, it can lead to pressure fluctuations and eventual drops.
- Recently bled radiators: If you've bled air from your radiators, the system will naturally lose some pressure and will need repressurizing afterwards. This is normal.
If you suspect a leak or a component failure, it's best to contact a qualified heating engineer to diagnose and fix the problem.
