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DIY Tip: How To Re-Pressurize a Combi Boiler

Those of us who have combi boilers may find, over time, that central heating and hot water on demand performance deteriorates.

Alternatively, you might find that, when you try to bleed your radiators, nothing happens.

Quite often, this can be due to a lack of pressure in the heating loop.

Pressurizing – or re-pressurizing – your combi boiler is a ludicrously simple task that may save you the hassle of calling out a plumbing and heating expert who will simply perform this task for you, and charge you a fee.

How To Tell If There is Insufficient Pressure In Your Boiler’s System

The simple way to check if your central heating system is under-pressured is to look at the pressure guage on your boiler. If it is below 1 bar, it could well be that you need to re-pressurize your boiler.

Check your manufacturer’s manual for specific details on the optimal pressure for your boiler. If you can’t find the manual, try searching online for the name and number of your boiler – this should be written on the boiler itself somewhere – as quite a lot of manufacturers put their manuals online.

But, as a rough rule of thumb, we’ll assume that optimal pressure is just over 1 bar. If your gauge is showing less than that – particularly if nothing happens when you open a radiator valve – then you need to re-pressurize.

The good news is this is really simple.

It should be faster to pressurize your combi boiler than it took me to write this, or you to read this.

Taps for Pressurizing Combi Boiler
Taps for Pressurizing Combi Boiler - in the "closed" position

How To Pressurize Your Combi Boiler

You may well need to pull the front cover off your combi boiler to locate the taps required to pressurize your system. This cover should just “pop” off. Give it a tug. Don’t panic, you shouldn’t be able to break anything just by pulling the front cover off!

There will be a flexible pipe leading from the cold water (mains) supply, to your boiler’s central heating loop.

At either end of this pipe will be a tap, which must remain in the closed position at all times – except when pressurizing the system.

To pressurize your system, first open the tap at one end of that flexible pipe. Then, open the tap at the other end.

You should hear water filling your central heating system.

You should see your pressure gauge first shoot up, then settle back and gradually increase. When it has gradually increased to the desired pressure, turn off the tap you just opened, then close the tap at the other end, too.

If you follow this up by bleeding your radiators, it makes sense to check the pressure again afterwards, as it may need a little more water in it again (after you let that air out!).

You should aim to keep the pressure at the optimal level, but this shouldn’t need regular maintenance, just a glance once or twice a year should be sufficient.

Any problems getting hot water on demand, or with your heating, and a quick glance at your pressure gauge is the first place to look.

Any Questions?

Leave your questions and comments in the comments section, below.

About Lifestyle Desk

Lifestyle Desk
Editors and staffers from the Lifestyle Desk at The Global Herald.

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