For those looking to address low boiler pressure, we have a helpful video tutorial. The guide, provided by one of the leading manufacturers, offers a step-by-step demonstration on how to safely and effectively repressurise your boiler. This resource can be a great way to resolve common pressure issues and ensure your heating system is working efficiently. We recommend watching the video for a clear visual guide on the process.

Please be aware some boilers are different.

Please see more detailed step by step instructions below.

Check Your Boiler's Pressure Gauge

First, locate the pressure gauge on your boiler. It will either be a hydraulic dial with a needle or a digital display. The ideal pressure for most boilers is between 1 and 1.5 bar when the system is cold. If the reading is below 1 bar, it's time to repressurise.

Instructions for an External Filling Loop

This is a flexible, braided silver hose that connects two pipes beneath your boiler.

1. Turn off your boiler. Switch off the central heating and allow the boiler to cool down completely to prevent injury from hot water.

2. Locate the filling loop. Check that the hose is securely attached to the two valves underneath the boiler.

3. Open the valves. Slowly turn both valves, allowing cold mains water to enter the system. You should hear the sound of water flowing.

4. Monitor the pressure. Keep a close eye on the pressure gauge as it rises.

5. Close the valves. Once the pressure reaches between 1 and 1.5 bar, turn both valves off. It's important to do this immediately to avoid over-pressurising the system.

6. Remove the filling loop. Disconnect the hose from the valves, as a small amount of water may drip out. Store it in a safe place.

7. Restart the boiler. Turn the boiler back on and check the pressure again.

Instructions for an Internal Filling Loop (Keyed or Keyless)

Many modern boilers have an internal filling loop, which is often a key or a lever built into the boiler itself.

1. Turn off your boiler. As with the external loop, switch off the heating and let the boiler cool down.

2. Locate the filling mechanism. This is often a key located in a small tray or a lever on the underside of the boiler.

3. Engage the mechanism.

   • For a key: Insert the key into the designated slot and turn it to the "open" or "unlocked" position as shown by the symbols.

   • For a lever: Simply pull down or turn the lever.

4. Listen for the water. You should hear water entering the system as the pressure begins to rise.

5. Monitor the pressure. Watch the pressure gauge carefully, stopping as soon as it reaches 1.5 bar.

6. Disengage the mechanism. Turn the key back to the "closed" or "locked" position and remove it, or release the lever.

7. Restart the boiler. Turn the boiler on and check the pressure gauge to ensure it remains at the correct level.

What to Do If Pressure Is Too High?

If you accidentally over-pressurise your boiler (the gauge reads above 1.5 bar), don't panic. You can release pressure by bleeding a radiator. This lets air and some water out of the system, bringing the pressure back down to a safe level.