How to Repressurise Your Boiler

Most modern boilers are pressurised systems. This means that instead of being topped up automatically from a loft tank, they rely upon being filled with the right amount of water from the mains. Consequently, owners need to check their water pressure gauges monthly. If it has fallen low (usually under 1.5 bar), you need to top it up again.

Some boilers display an error code when pressure is low. Identify fault codes here:

Modern boilers make it easy to do the job yourself without calling out a service engineer. However, even if you never see a problem, you should still get an annual service.

When to Call an Engineer

If your boiler has lost pressure suddenly, you could have a leak. Check beneath all your radiators for wetness, but leaks can also be hidden or outside the building if pipes travel along external walls.

Bleeding air from radiators slightly reduces the pressure in the system, but if you are having to do this frequently, there is something else amiss and you may want an engineer to track the problem.

Annual safety inspections don’t include a full service. Whether you are gas or electricity powered an annual service makes sense. A Gloucester boiler service is available from

Topping Up Your Boiler

Always check your manual, but most pressurised boilers provide one of two top-up methods.

Combination boilers often provide a key, which is frequently found attached to the inside of the removable bottom boiler panel. At the bottom of the boiler you will see the ends of two pipes. One is already fitted with an easy to turn valve – your key fits into the other. Insert and turn this key. Then turn on the other pipe too. You will now hear the water entering. As soon as you reach the recommended pressure, turn off the valve, and then turn off and replace the key safely.

The other common type of boiler uses a flexible loop to connect the boiler to the mains inlet pipe. It may already be attached, or you may need to fit it yourself. Hopefully, you will have been left with the hose to do the job and a supply pipe within easy reach. The valve may need a screwdriver to turn it. Turn it back off when your gauge reaches the right level.