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Just like checking the air pressure in your bicycle tires, maintaining the correct pressure in your central heating system is an essential maintenance task. While most systems only need repressurising once or twice a year, it's easy to forget the process when you need it most. This guide will walk you through how to safely repressurise your system, no matter what type of filling loop you have.

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When Should You Repressurise Your System?

If your boiler suddenly stops working and displays a fault code (such as E118 or E119), this typically indicates that the system pressure has dropped below 0.5 bar and needs topping up with water. This is a normal occurrence, as boilers work hard throughout the year to provide heating and hot water.

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Before You Start

Before repressurising your system:

1. Locate your boiler's pressure gauge
2. Turn off power to the boiler at the fuse spur (usually located near the appliance) or unplug it if it's connected to a socket
3. Identify which type of filling loop you have (there are several common variations)

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Types of Filling Loops and How to Use Them

1. Green Lever System

This is one of the simplest systems to use:

• Look underneath the boiler for a green lever on the right-hand side
• Pull the lever down until you hear water entering the system
• Watch the pressure gauge - when it reaches the top of the green zone (around 1 bar), release the lever
• It's normal to see a few water drops after releasing the lever
• Turn the power back on to resume normal operation

2. Double Blue Tap System

This system requires a bit more setup:

• Locate the two blue taps under the boiler on the right side
• Remove the brass caps from the filling loop
• Install the copper bend with rubber washers and brass wing nuts
• Open the left tap first (cold mains side)
• Slowly open the right tap until you hear water flowing
• Monitor the pressure gauge until it reaches the green zone
• Close both taps in reverse order
• Remove the copper bend and replace the brass caps

3. Flexible Braided Hose System

Often found with system boilers, this type might be located near the cylinder:

• Look for a silver flexible hose with a pressure gauge nearby
• Use a flat-blade screwdriver to open the first valve (turn so the line aligns with the pipe)
• Slowly open the second valve until you hear water flowing
• Monitor the pressure gauge until it reaches around 1 bar
• Close both valves and check for leaks

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What If You Over-Pressurise?

If you accidentally add too much water, don't worry. You can reduce the pressure by:

1. Using a radiator bleed key and old towel
2. Turning the radiator vent key a quarter turn anti-clockwise
3. Catching any water in a container
4. Closing the vent once the pressure gauge shows the correct level

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Important Tips

• Take your time when repressurising - it's better to add water slowly than risk over-pressurising
• If you notice an unusual smell when bleeding radiators, this might be the system inhibitor - mention this to your heating engineer
• If you're finding yourself frequently repressurising the system, contact a professional as this might indicate a leak

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Need Help?

If you're unsure about any aspect of repressurising your heating system, don't hesitate to contact JLN Plumbing & Heating Limited. Our experienced team is always happy to provide professional advice and assistance.

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