Last Updated on 23rd August 2022

What Are Most Common Boiler Faults

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A faulty boiler sounds like a nightmare scenario for any household. It’s not much fun being stuck in a cold home with no hot water. Although modern boilers are relatively reliable, every boiler is bound to break down at least a couple of times during its lifetime. Even the most reliable boilers do break down – the question is how long is your manufacturer warranty period, how clued up is your heating engineer and how well you maintain your central heating boiler.

On average, outside of the manufacturer’s warranty period, each callout to a faulty boiler will cost you between £150 and £250 depending on what’s broken. Wrong choice when picking a new boiler model may end up costing a lot of money. One of the most widespread marketing messages in the boiler industry is that you can save a lot of money on fuel bills by installing a new A-rated boiler, however, if you get the wrong boiler, the expected savings may turn into unexpected expenses.

Have a look at out combi boiler comparison charts to see which ones offer the longer warranty periods. Another source of information is the annual boiler reports by Which – the consumer association testing consumer goods and publishing unbiased reviews on their findings. Worcester Bosch, Vaillant and Viessmann always appear within the top of their boiler reviews, however, the warranty period is different depending on who your installer is. Also the warranty terms may be different, so make sure your warranty includes all parts.

Boiler maintenance, as we mentioned before, is very important in keeping your costs down. Most common boiler faults surprisingly don’t include heat exchanger – the part that most people have heard of. It is actually the circuit board that fails more often. Incidentally, it’s also the most costly repair job – on average costing nearly £280 to put right. The cheapest and less costly repair job involves replacing a thermocouple – it only costs £80 – £90 to fix. The complete list of the most common boiler faults is included below.

  1. Circuit board – £270 – £280
  2. Combustion fan – £230 – £250
  3. Diverter valves – £180 – £200
  4. Ignition system – £100 – £120
  5. Gas valve – £210 – £230
  6. Pressure relief valve – £100 – £110
  7. Automatic air vent – £90 – £100
  8. Water pump – £200 – £220
  9. Thermostat – £100 – £110
  10. Thermocouple – £80 – £90

Some boilers are so badly maintained that they can easily have a string of these repairs close by or even at the same time, making the repair bill skyrocket to ridiculous proportions. The best advice that can be given on boiler maintenance is making sure the boiler doesn’t overheat by working harder than necessary. Make sure your water temperature is not set to higher than 65C. Anything higher than that is really unnecessary.

Also it’s worth checking the radiators and venting the air out regularly. A tell-tale sign that there’s air or sludge present in a radiator is that its top/middle part is cooler than the edges. If you vent out the air and the middle is still cooler, it means there is sludge in the radiator. In this situation, the boiler will have to work harder than normal to keep the room temperature up.

It’s important to set your room thermostat to an optimal temperature. Be comfortable but don’t overheat the house. That way not only you will save money on fuel bills, you will also increase the work life of your boiler. Put the thermostat in the room that’s the warmest and most sheltered. If you place your thermostat in the coolest part of your house, the boiler will again work harder and your warmer rooms will overheat.

These simple tips will ensure that the most common boiler faults are going to be few and far between and help you save money on repair bills.