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Trouble Shooting

Boiler pressure too high? We explain how to fix it

The water pressure inside your boiler should be between 1 and 2 bar. If you look at the pressure gauge on the front of the boiler when it is working, the needle should be in the green area.If the needle is creeping into the red area, it means the boiler pressure is rising and needs your attention.

Signs your boiler pressure is too high

The most obvious sign that your boiler pressure is too high is the reading on the pressure gauge on the front of the boiler.If the pressure gets too high when the heating is on, the pressure relief valve (PRV) may be triggered, and you may see water dripping from a copper pipe, which is usually located outside. Some boilers may also have an error code to indicate high pressure.Check your user manual to see if your model has a high pressure error code.

Why is my boiler pressure too high?

There a several reasons why your boiler pressure is too high.

  • A radiator has been removed, for example while decorating a room, and the system was overfilled when it was replaced.
  • The water pressure was low and was topped up too much.
  • Check that the filling loop is completely closed and not letting more water into the system.

If the water pressure continues to be high after bleeding the radiators (see next section), please call your heating engineer or Baxi Customer Support to check your heating system is safe to use.

Is high boiler pressure dangerous?

High boiler pressure is not dangerous because the boiler has a pressure relief valve (PRV) that opens if the system pressure gets too high so that water can escape safely.However, if your boiler pressure keeps creeping up, it’s a sign that something could be wrong. Please call your heating engineer or Baxi Customer Support so they can come and check your boiler.

What to do if your boiler pressure is too high

The best way to reduce the pressure in your boiler is to bleed the radiators. Before you start, make sure your central heating system is switched off. You’ll need the radiators to be cool enough to handle. Some modern radiators can be bled with a screwdriver. However, for most types of radiator, you’ll need to use a radiator key.

  1. Attach the radiator key into the square section in the centre of the radiator valve
  2. Use a cloth or strong tissue paper to hold the radiator key
  3. Have another cloth under the radiator valve to catch any drips
  4. Turn the radiator key slowly in an anti-clockwise direction
  5. Allow water to leak out of the valve until the pressure gauge on the boiler returns to 1.5 bar
  6. Close the valve quickly by turning the radiator key
  7. Check the pressure gauge on your boiler. If it’s too low you’ll need to top up the pressure again. You can do this by watching our videos here. 
What to do if your boiler pressure keeps rising

If your boiler pressure keeps rising, and you have checked everything in the sections above, please call your heating engineer or Baxi Customer Support so they can come and check your boiler.

What is a pressure relief valve?

The pressure relief valve (PRV) is a safety valve that prevents the pressure in the heating system building up to a dangerous level.  It opens if the pressure gets too high and closes again when the pressure returns to normal.  If it opens, you may see water dripping from a copper pipe that goes from the boiler through an outside wall.  If water continues to drip, the valve may not be closing properly because the system water contains tiny bits of limescale or debris that could be getting caught in the valve.  Your heating engineer or Baxi Customer Support engineer can clean this easily when they carry out the boiler’s annual service.

If you are worried that your boiler pressure is too high, please contact your Gas Safe registered heating engineer or call Baxi Customer Support.

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