Refilling central heating boiler

Refilling the central heating boiler

If the radiators in your home don’t heat up as much as they used to, or the temperature of your tap water fluctuates, it could be possible it is time for you to refill the central heating boiler. The right water pressure in your boiler is necessary to circulate the water through the heating system of your house. When the water pressure is too low, the water no longer correctly flows to the radiators. Not only does this prevent your radiators to heat up as they should, it could also be the cause for the pump of the central heating boiler to break. Therefore, it is wise to check the water pressure of your boiler every three months. You should refill the boiler, when the pressure is less than 1.2 bar. The correct water pressure for the boiler is between 1.2 and 2.0 bar. You will probably also need to refill the central heating boiler, after you’ve vented the radiators. If you have to refill the boiler more than usual, there could be a leakage in the heating system. If that’s the case, please contact us.


  • A bucket
  • A cloth
  • The filling hose

How to

  • Connect the filling hose to the water tap. There should be a tap near your boiler.
  • Make sure there’s no air in the filling hose. You can do this by opening up the water tap, and let the water run until it runs into the bucket. Take the hose and hold it up. You can now close the tap.
  • Connect the other end of the filling hose to the boiler. The opening should be beneath the boiler.
  • Open up the water tap and the filling tap on the boiler. You are now refilling the central heating boiler with water. Keep a close eye on the water pressure gauge. If it shows the pressure in the boiler is 2.0 bar, close the water tap and the filling tap. You can catch whatever water is left in the hose with the bucket.
  • After refilling the boiler, you should also vent the heating system. Here’s a description of how this venting works.

Here you can go to a video about how to fill the boiler. Change the subtitles to English.

Instruction video on refilling central heating boiler

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