One of the most common boiler faults is low boiler pressure (Ideal boilers F1, Vaillant boilers F75 F74 F73). It is normal for the central heating system to lose pressure over a period of time. If you have bled your radiators recently, pressure could be lost due to that. (Follow our guide on how to top up your radiators). It may be that there is a leak somewhere in your heating system. Sometimes leaks can be so small that they’re unnoticeable. It is recommended that you check your boiler pressure at least once a month to help reduce the chances of unexpected boiler breakdowns.

Your central heating boiler must have an operating pressure between 1 bar and 2 bar. Being at this pressure keeps the central heating gas boiler (combination boiler, system boilers and heat only boilers that are sealed via an expansion vessel) and central heating system free from air. If the pressure drops below the normal boiler pressure level, a safety switch is activated that cuts the boiler off – this is done to prevent damage to the central heating system and boiler. It also prevents both the central heating system and boiler from running dry (with no water circulating).

If your boiler has low pressure, you can top up your system and have your boiler working within a few minutes by following the steps below:

1. Look for the filling loop under the boiler. It will connect between 2 pipes. There are a few variations of filling loops, and for your reference we’ve included an image of a common filling loop below
2. On each end of the filling loop there will be a valve which should be closed. This can be checked as the valve handle has to be positioned horizontally across the filling loop .
3. Are the valves in the same position? If they are not, operate them so they are both horizontal.
4. Open one valve fully and then open the second valve slowly. Keeping your hand on the valve, you will hear the water entering the boiler. Watching the pressure gauge, you will see the black needle rising. Ideally the pressure should be 1.5 bar, or the needle should be at the 10 o’clock position.
   When the needle reaches the desired position, close both the valves and reset the boiler. You should now have central heating and hot water .It’s normal to top up your boiler every few months, but if you find you have to top up the boiler every day or every week, and if you have HomePolicy cover, please call us on 02089878031 or email info@HomePolicy.co.uk and report a fault and arrange for an engineer to attend.
5. The boiler pressure gauge will normally be located on the front panel or underneath the boiler. The pressure gauge may also be digital on certain boilers, this can be found by pressing the information button continually until the screen displays a bar reading.
6. Join HomePolicy today if you’re not already a member and allow us to do all the work for you.

We’ve included some helpful links on topping up the pressure for some of the most common boiler brands. If your boiler is not listed, enter your boiler make with the phrase “top up boiler pressure.” For example: “Baxi boiler how to top up pressure.”

• Topping up pressure on a Glowworm boiler
• Topping up pressure on an Alpha boiler
• Topping up pressure on a Viessmann boiler
• Topping up pressure on a Vaillant boiler
• Topping up pressure on a Baxi boiler
• Topping up pressure on a Worcester boiler
• Topping up pressure on a Glowworm Ultracom
• Topping up pressure on an ATAG boiler