If your heating isn’t working after bleeding your radiators, you may need to top up the pressure in your boiler. This is a simple solution that can get your heating back up and running quickly, just follow our step by step guide.

Most of our homes have boilers that are topped up using an internal filling key. You can also watch this video showing how it’s done.

To get started, check the pressure gauge on the front. If it’s dropped below the green and into the red you should follow the steps below.

  1. Turn power off to the boiler
  2. Remove the tray beneath your boiler. The internal filling key should be attached to this tray. If it isn’t attached, let us know.
  3. Underneath your boiler look for the black plastic manifold, an opening where you will insert the internal filling key.
    There should be two symbols on the manifold, a closed padlock and an open padlock.
  4. On the key, there is a small arrow. Insert the key into the opening with the arrow pointing at the open padlock.
  5. When the key is in place, turn it so the arrow points at the closed padlock.
  6. Turn the white plastic nut next to where you have inserted the key anti-clockwise. When you do this, you should begin to hear water filling into the heating system.
  7. Watch your pressure gauge as the needle should be rising.
  8. When the pressure is in the green and has reached 1.5, turn the white plastic nut back clockwise, until you hear the water stop.
  9. Turn the internal filling key back to the open padlock position.
  10. Remove the internal filling key. Aa few drops of water may drip out – this is normal. If water continues to trickle out, the white plastic nut hasn’t been closed tight enough.

If your boiler isn't topped up with an internal filling key, you will top it up using an external filling loop. You can find a video tutorial for topping up your boiler pressure with an external filling loop here.

If you have topped up your boiler pressure too high and your pressure gauge has gone into the red, don’t panic. This can easily be solved by bleeding your radiators to take pressure back out of the system.

If you’re not sure how to bleed your radiators, you can follow our step by step guide.


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