Vokera boiler pressure

How to Repressurise Vokera Boiler Pressure

Last updated on February 19th, 2024

When your boiler pressure drops too low the boiler will stop working which means you will have no heating or hot water.

Vokera boiler pressure should be between 1 and 1.5 bar on the pressure gauge when the radiators are cold.

I have been repairing and servicing boilers for over a decade and have fixed many boiler pressure problems.

Vokera Boiler Pressure

If your Vokera boiler pressure is under 1 bar then you should increase the pressure.

If your Vokera boiler pressure is over 1.5 bar when the system is cold, then you should reduce the pressure.

Boiler Pressure When Heating On

The boiler pressure when the heating is on can rise to over 2 bar. This is perfectly normal as the heat expands the water inside the central heating system when the heating is turned on.

Vokera boilers have a pressure relief valve which is set at 3 bar. If the boiler pressure reaches 3 bar then the water will be let out as a safety precaution and the pressure will drop to zero bar.

How to the Check Pressure

You need to find the pressure gauge to check the pressure on a Vokera boiler.

How to Increase the Pressure

If your Vokera boiler pressure drops below 1 bar you will need to increase the pressure.

To increase the pressure on a Vokera boiler you must:

  1. Open one valve fully (only if there are two valves)
  2. Open the other valve slowly until you can hear the water
  3. When the pressure has reached 1 to 1.5 bar close both valves
  4. Reset the boiler (if needed)
  5. Turn the heating on

Do not open both filling loop valves fully straight away as the water pressure in the house might be too much for the boiler and cause the Baxi boiler pressure to shoot up too much.

Boiler Pressure Too High

Your Vokera boiler pressure is too high most likely for one of these reasons:

  • Somebody repressurised the boiler too much: Reduce pressure in the boiler by letting water out
  • The expansion vessel has lost air or the diaphragm inside is split: Recharge or replace the expansion vessel
  • The filling loop is not closed fully or damaged: Close the filling loop fully or replace it
  • Pinhole leak on plate heat exchanger on a combi boiler: Replace the plate heat exchanger

How to Reduce Pressure

To reduce boiler pressure you must let some air or water out of the heating system.

Here are the 5 best ways to reduce pressure:

  • Bleed a radiator
  • Open a drain off valve
  • Open the pressure relief valve
  • Crack a nut
  • Magnetic filter

Bleed a Radiator

The easiest way to do this is to bleed the radiators using a radiator bleed key. You should bleed all the air out of all the radiators.

When there is no air left, you can bleed the water out of one radiator until the pressure drops to 1 to 1.5 bar.

Put a towel or two down on the floor under the radiator and catch the water squirting out into a bucket.

Open a Drain Off Valve

Most central heating systems have at least one drain-off valve. You can find them on radiator valves, radiator pipes, and on the bottom of boilers. They are for draining water out of the central heating system.

You can connect a hose to a drain-off valve using a hose clamp and run the pipe to an outside drain or down the toilet or sink, then open the square nut using an adjustable spanner until the water starts coming out.

Keep checking the pressure gauge on the boiler until it has dropped to around 1 to 1.5 bar.

Open The Pressure Relief Valve

Another way to reduce boiler pressure without bleeding radiators is to open the pressure relief valve.

A pressure relief valve is on every pressurised central heating system.

They are usually inside the boiler but could potentially be in the hot water cylinder cupboard.

You simply turn it anti-clockwise (or pull the lever on some boilers), and the pressure will drop very quickly.

This is the easiest way to reduce boiler pressure without bleeding radiators and the most common way I do it when I’m on a job.

The only problem with opening the pressure relief valve is that once they’ve opened they might not close again properly.

This will tend to happen on dirty systems but 9 times out of 10 it’s fine. If it does happen, you need to change the pressure relief valve.

Crack a Nut

Cracking a nut is another way to lower the pressure without bleeding radiators when your boiler pressure is too high. This is one of the messiest ways to do it but it is possible.

You can put towels and a bucket under a nut on the boiler, radiator valves, or anywhere on the central heating pipes.

Then crack the nut until water starts coming out and keep an eye on the boiler pressure gauge.

Magnetic Filter

It is also possible to reduce boiler pressure via the central heating magnetic filter.

You should place a towel and bucket underneath the magnetic filter then open the nut on the bottom (if it has one) or you can open the bleed valve with a bleed key.

Let the water come out into the bucket and close it when the pressure gauge has dropped to around 1 to 1.5 bar when the system is cold.

Boiler Pressure Too Low

Low boiler pressure is very common and can cause your boiler to stop working. If your Vokera boiler pressure becomes too low then you need to repressurise it.

Boiler Keeps Losing Pressure

Your Vokera boiler losing its pressure is most likely for one of these reasons:

  • A Leak on the central heating system
  • The expansion vessel has lost its air
  • Pressure relief valve passing water
  • Filling loop open

Vokera Boiler Guides


If your boiler pressure is too low or too high then fixing this is important. Repressurising a Vokera boiler is an easy job. It can save you from having to pay a plumber to do such an easy task.

If you have to keep repressurising your boiler, you should get that problem found and fixed as soon as possible.

Feel free to ask me any questions in the comment section below and I’ll do my best to help.

Please share this post if you find it helpful.


  • Steven Reid

    I am a full-time plumber and Gas Safe registered engineer. I incorporated Housewarm Ltd. in 2011 to provide heating and plumbing services to homes in Newcastle upon Tyne, England. I now blog about what I've learned over the years to help DIYers and plumbers.

    View all posts
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3 thoughts on “How to Repressurise Vokera Boiler Pressure”

  1. Victoria

    My Vokera loses pressure slowly. We replaced the expansion vessel and the pressure now drops quicker (goes from 1.5 to 1 bar in a week). The boiler is used for underfloor system and when the pressure is low we actually can hear how air circulates in the system and gets louder as the pressure drops. We don’t see any signs of leak. The pressure never goes up or over 3 bar either when the system starts. Now we are thinking of replacing the pressure relief valve. Unfortunately the clip that holds it in place is stuck and we are not able to move it. Any suggestion on how to remove the PRV and the pin/clip without damaging the plastic around the clip? Any other suggestion on what else might cause the pressure drop? Thank you!
    And thank you for all the useful details you share in your post.

    1. Steven Reid

      Hi Victoria,
      You should see water coming out the copper pipe outside if it’s the pressure relief valve that’s causing the pressure to drop, I wouldn’t replace it if there’s no water coming out.

      You’ll have to force the clip out somehow, I’d have to see it to give you specific recommendations but large water pump pliers usually help.

      It could be the underfloor heating that’s leaking, if you’ve got any isolating valves to isolate it from the rest of the system you should do that and see if the pressure keeps dropping, if not you could get some iso valves fitted.

      You should isolate the boiler from the system first though, top the pressure up to 1.5 bar then close the flow and return valves on the boiler and leave it for as long as it takes to usually drop, if it doesn’t drop then you’ll know it’s on the heating system and not the boiler.

  2. Brigitte

    We have a Vokera Excell 80 Sp boiler that has been in place for about 20 years+ from what we can understand. We only moved in a year ago.
    It keeps losing pressure and sometimes but not everytime there is water underneath the boiler. If we repressurise it it loses pressure within a couple of hours. The pipe outside looks dry although I do intend to do your bag check. We had a plumber or two in to look and they said replace because parts are expensive. What do you think we should attempt of your above things before giving in and getting a new one. We are in Scotland.
    Do you think by opening the valve to put more water in we have upset the balance and hence it keeps dropping pressure?
    Neither of the plumbers looked at the expansion vessel or checked that for air vs water.
    We would like to DIY fix it if possible.

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