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Boiler problems you can fix yourself

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Boiler problems you can fix yourself

If something goes wrong with your heating, especially during a cold spell, you want it to be fixed as quickly as possible. Although for most problems you should call a qualified heating engineer, there are some things that you can definitely do for yourself, however DIY-minded you are! 

Doing those things will get your system back working more quickly and, of course, avoid needless call-out charges so saving you some money.

Low water pressure

 If your central heating isn’t working properly, it could be because your boiler’s water pressure is too low.

You’ll find a water pressure indicator on the front of your boiler, and in normal use it should read between one and two bars of atmospheric pressure. If the number has dropped below one, then you have low water pressure and this needs to be fixed.

Turn off your boiler and allow the system to cool. Then find the filling loop, a flexible hose under the boiler. The hose will have a valve at both ends which can be opened using a screwdriver. Open both, and you should hear the sound of water from your cold water supply filling the system. When the pressure gauge reaches 1.5 bars, then close the valves again.

At that point, you can switch the boiler back on. You may need to reset it.

If you do this, and you see no change in the dial, it may be broken. In that case, you’ll need to call out an engineer.

High water pressure

 Just as low pressure can impair the effective working of your system, so too can overly high pressure. In this case, if your gauge is colour-coded, the dial will be in the red or if it’s simply a number dial it will be above 2.

The way to reduce the water pressure in the system is to bleed some of the water (and probably air) from the radiators. First of all, you’ll need to turn off the boiler and allow the system to cool down.

Then, you should ideally have two people on hand for the next part. Starting with ground floor radiators, bleed some of the water out using the radiator bleed key (or screwdriver for modern radiators) catching the excess water in a bowl. While one person is doing this, the other can be at the boiler watching the dial go down so they can see when it reaches the 1.5 bar sweet spot. Once it has, then you can stop, and restart the boiler as normal. 

Once again, if you bleed the radiators and there’s no movement on the dial, it probably means the dial is broken and you should call a heating engineer.

System reset

 If the boiler’s not working, you can try a system reset. Each boiler will have a reset button – check your boiler’s manual for the location of yours (or check online – this information is mostly easily findable these days).

Often, you will need to hold the reset button for up to ten seconds for it to be effective.

Oil boiler not working after having run out of oil

If your oil tank ran out of oil, you may sit shivering in your home until the company refills your tank, and which point you run delightedly to switch the heating on – only to find that nothing happens.

What’s happened is that air has become trapped in the pipe that transports oil to the boiler, and it needs to be bled out of the system before the boiler can begin working. 

Your boiler will have bleed nut on the front – consult the manual for your boiler to see where it is. You may need an allen key, or just a screwdriver, to unscrew the plug. You don’t want to remove it completely, just so you hear the hiss of escaping air. Within a few seconds, you’ll get a dribble of oil (catch any residue with rags), at which point you can loosely close it and try to fire up the boiler again. If it tries to get going, but then fails again, you just need to repeat the process a few times until you’ve gotten through all the air.

It can take multiple tries before you finally get the satisfying ‘thump’ as the system kicks in and the burners find the fuel they need. At that point, fully tighten the plug. Job done.


If these steps didn’t help, then contact us and we’ll get your boiler back up and keeping you warm.

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