How to top up your boiler pressure

Your home boiler is a vital component in ensuring a warm and comfortable living space, especially during the chilly months. However, like any other appliance, boilers require regular maintenance to operate efficiently. One common issue homeowners encounter is a drop in boiler pressure. Fortunately, topping up your boiler pressure is a straightforward task that can be done without professional assistance. In this guide, we’ll walk you through the steps to help you maintain optimal boiler performance.

Your heating system can lose pressure over time due to various reasons. This is a common issue and should not be a cause for concern. However, understanding how to re-pressurise your system is crucial to ensure its optimum performance.

Why do you need to know how to top up your boiler pressure?

There are several reasons why your heating system may lose pressure and require topping up:

  • Your control unit may flash a fault code which represents low flow or low pressure.
  • You have manually bled the radiators of any air, which reduces the pressure.
  • Air has been bled automatically via air vents installed as part of the system.
  • Your anti freeze valves have operated due to extreme cold weather, partially draining the system.
  • The system has a leak.
  • The system has a fault and a safety device has triggered to relieve the pressure.

How do I know what pressure my system should be?

Your heating system is fitted with a pressure gauge and filling loop (see image 1). This is a flexible hose or pipe that connects the cold water mains to the boiler. This is where you’ll be adding water to increase the pressure. Familiarise yourself with the filling loop and its connection points before moving forward.

Your system should ideally be set to run between 1.0 Bar & 1.5 Bar. The system pressure will fluctuate slightly with the system temperature due to expansion.

What do I do if my system loses pressure?

  • Visually check for any signs of water leaks. Contact us of you have a leak and take no further action. If no leaks proceed.
  • Top up system pressure using filling loop as per instructions of use below.
  • Check radiators for air by bleeding them with a vent key.
  • Top up system pressure as needed.
  • Reset any controls showing a fault code if required.

Filling the system

1. Ensure all joints are water tight.
2. Follow the instructions supplied with the boiler for filling the heating system. If you can’t find these you can check the manufacturer’s website for instructions. Open valve (4).
3. Use valve (2) as a regulating valve by partially opening slowly, whilst reading the pressure on gauge (1) until the required pressure has been achieved approximately between 1 and 1.5 bar.
4. Once filling and pressurisation have been completed, close the ball valves (2) and (4).



Maintaining the proper pressure in your boiler is a simple yet essential task to ensure its efficiency and longevity. By following these easy steps, you can confidently top up your boiler pressure and keep your home warm and comfortable throughout the year. Remember, if you encounter any issues or are unsure about the process, it’s always a good idea to contact us for assistance.

Still need help with how to top up your boiler pressure?

If you need further assistance with how to top up your boiler pressure or have any queries, don’t hesitate to reach out:

Contact Number: 01404 234363

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