How to get water pressure in your boiler

Written by victoria gorski
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How to get water pressure in your boiler
Check radiators and piping for leaks before adding water pressure. (white radiator image by Ekaterina Sidorenko from

A boiler must have enough water pressure to push heating through each radiator in a home efficiently; if the pressure drops the heating system will not function properly and the boiler may even shut off completely. Boiler pressure is normally between 1 to 1.5 bar when cold and or 2 to 2.5 bar when the heating system is in use. When pressure is lost in the system this can normally be due to leaks, cold weather or just because the pressure will reduce over time. Water pressure can increased without an engineer to keep the heating system running to optimum capacity.

Skill level:


  1. 1

    Briefly check the radiators and any visible pipes from the heating system for leaks. If there is a leak in your system you should contact your manufacturer as it makes increasing the water pressure ineffective.

  2. 2

    Switch off the heating system on the boiler (or turn the temperature of the radiators down on the boiler controls until completely shut down). Check the pressure gauge on your boiler; this should be below 1.5 if your system needs refilling.

  3. 3

    Locate the filling loop. The filling loop is a flexible loop between the boiler and the "water in" copper pipe. A filling loop has a knob in the middle of the flexible pipe and normally "hangs" down from the boiler and attaches to another pipe.

  4. 4

    Twist the knob on the filling loop clockwise. You will hear a hissing sound or the sound of running water as water pressure is added. Watch the pressure gauge as you add water pressure and ensure the pressure does not rise over 2.5 bar.

  5. 5

    Close the filling loop by turning the knob counter-clockwise once water pressure has been added.

Tips and warnings

  • If you do not have a filling loop on your boiler you should contact your manufacturer or engineer to add water to the boiler.

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