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Easy Guide to Re-pressurising your Boiler

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Follow this simple guide on re-pressurising your Boiler

Bleeding a radiator involves releasing any trapped air inside it. Doing so helps improve the efficiency of your heating system. This guide is designed to walk you through the safe steps of bleeding your radiators and re-pressurising your boiler. If you have any doubts or concerns, it’s best to consult a qualified professional.

Re-pressurise your boiler

Why Re-Pressurising Your Boiler Matters

Maintaining the correct boiler pressure is essential for keeping your central heating system running efficiently. When pressure drops too low, your radiators may not heat properly, your hot water may cut out, or your boiler could shut down entirely. Fortunately, re-pressurising your boiler is a straightforward task that most homeowners can manage themselves, as long as you follow the proper steps.

Whether your boiler has a keyless or keyed filling link, knowing how to safely top up the pressure helps prevent cold spots, avoids unnecessary callouts, and can extend the life of your boiler. Low pressure is often caused by bleeding radiators or minor water leaks in the system, both common issues, especially during colder months.

This guide will show you how to re-pressurise your boiler correctly, step by step. However, if the pressure continues to drop after re-pressurising, it could indicate a deeper fault that requires attention from a professional. Always contact a Gas Safe engineer if you’re unsure or need expert support.

Keyless Filling Link

  • If the pressure gauge needle is below 1 bar, the system needs to be re-pressurised.
  • Lower the blue lever to begin filling the system.
  • Keep an eye on the pressure gauge as the system fills.
  • Once the needle reaches between 1 and 1.5 bar, release the blue lever to stop filling.

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    Keyless filling link

    Integral keyed filling link

    Locate the filling key and follow the instructions for re-pressurising.

  • Insert the filling key firmly into the filling link, making sure the arrow on the key shaft aligns with the open padlock symbol.
  • Turn the key to the right until it stops, ensuring it is fully locked and cannot turn further. The arrow should now point to the closed padlock symbol, connecting the two parts of the filling loop.
  • Turn the white knob to the left to allow water to enter the system.
  • When the pressure gauge on the appliance fascia shows a reading between 1 and 1.5 bar (zone A), turn the white knob to the right to close the valve. Avoid overtightening.
  • Turn the filling key to the left until it stops, so the arrow points to the open padlock symbol, then pull the key straight down to remove it. Be sure to store the key in the bottom panel.

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    Keyed filling link

    Does your boiler lose pressure daily?

    If your boiler is constantly losing pressure and you find yourself topping it up regularly, this indicates a problem — it shouldn’t be happening. Before checking for leaks in your system, there’s one important step to take: check your pressure gauge while the heating is on.

  • Does the pressure gauge rise significantly before the heating begins to cool down?
  • Is there a copper pipe on the outside wall that’s dripping or spraying hot water?

    • If you can see one or more of these errors your expansion vessel inside your boiler may need recharging or replacing. This has to be done by a Gas Safe registered engineer, this fault is very common across every boilers brands. Boiler servicing should include to check and recharge your expansion vessel, so this fault could be fixed by getting your boiler serviced.

    Get your boiler serviced by or friendly, expert team at Koziwarm, Get in touch with the team today.

    Koziwarm Heating Installers, Colchester
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