Steps on how to Re-pressurise Your Boiler
Re-pressurising your boiler every now and again is an important maintenance job that helps to keep your boiler healthy. Whether you have a system, a combination or a combi boiler, re-pressurise it regularly and you’ll be heating your home more efficiently, extending the life of your boiler and helping to cut down any potential engineer costs.
If you find your central heating system isn’t working as it should, it’s possibly due to a loss of water pressure. But before you pick up the phone to call out a professional, why not find out how to re-pressurise your boiler yourself?
To increase the pressure in your system, you’ll need to use a filling key or filling loop (filling hose), depending on the age and type of boiler you have.
Re-pressurising your boiler using a filling key
It’s important to switch your boiler off before re-pressurising it. If possible, let it cool down for 4 to 6 hours.
Carefully pull out the tray underneath your boiler and remove the key attached to it. You may find the key is secured to the tray with a clip. If so, unclip it to remove.
Next to the square manifold nut, you’ll find the key manifold keyhole. Insert your filling key into the key manifold.
Turn the key approximately 45 degrees to the unlocked position.
As the pressure begins to rise, the arm on your boiler’s pressure gauge will begin to move up. Turn the manifold nut clockwise when the gauge reaches 1.5 bars. Keep an eye on the gauge to make sure it settles at this pressure.
If the arm moves into the red section on your gauge, don’t panic! Turn the release knob on a nearby radiator and this will quickly lower the pressure on your boiler.
If you need to do this, take care not to be too close when turning the release knob on the radiator — the release valve will emit hot air.
When you’ve turned both the manifold nut and the manifold key back to the locked position, remove the filling key and put it back in the tray underneath your boiler.
Switch your boiler back on. The pressure may fluctuate slightly at first, but it should settle within a minute or two.
Re-pressurising your boiler using a filling loop
Switch your boiler off and allow 4 to 6 hours for it to cool down. When your boiler has cooled, check the filling loop hoses are secure (they may need tightening).
A radiator, expansion tank or pressure relief valve leak could also cause a pressure drop, so it’s worth checking these things, too.
Open the filling valves. These can be unlocked by tap handles, or with a screwdriver, and will be found near to where the filling loop hoses connect to the boiler. As you turn the valve counter clockwise, you should start to hear water.
When the pressure gauge on your boiler reaches 1 bar, it’s time to close the valves.
When the pressure on the gauge has settled at 1 or 1.5 bars, switch your boiler back on.
Once you’ve topped up the pressure on your system, your boiler should be working well — successfully heating your home and giving you plenty of hot water. But if it begins to lose pressure again, or you don’t have the time to give it a go yourself in the first place, call a boiler repair engineer.
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