By far, the most popular type of boiler in the UK today is a Combi boiler. This type of boiler gets its name because it undertakes two different jobs, it provides heating for your home and hot water. Combi boilers are reliable, efficient and do not take up as much space as a traditional boiler.

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However, considering that they are a critical component in the home and used 24 hours a day, seven days a week, it is inevitable that problems will develop at some point during their lives. 

One of the most confusing problems that can crop up occasionally is when the boiler is not heating up the water, but the heating system is still working, or vice versa. Although this can be frustrating, the good news is that there is unlikely to be a significant problem with your boiler, because typically you will have a boiler not working or its working and the problem is elsewhere.

If your boiler is still functioning sufficiently to power the heating system, it is unlikely that the fault lies in the boiler itself. 

Let’s assume that you have no hot water but that your heating is working perfectly, so it is safe to assume that you do not have a boiler losing pressure. Below is a step-by-step process you can follow to identify the problem and resolve it. 

Check Your Boiler For A Fault Code 

Nearly all boiler manufacturers build an LCD panel into their which is designed to display a fault code. This fault code should direct you to the nature of the problem quickly and efficiently. Even if you cannot find the operating manual that came with your boiler, a quick internet search should help you work out the issue.

Just ensure that you check the code for your exact boiler model, as the codes can vary even with the same manufacturer. If you cannot determine what a specific code means, then you should contact the manufacturer direct, or alternatively, call a Gas Safe engineer for advice. The codes could mention a range of different issues, including no pilot light, low boiler pressure, or the burner being blocked, for example. 

Check Your Gas, Electricity and Water Are All Working Properly 

In many situations, the problem can be something straightforward and easy to fix. Rather than waste a lot of time checking potentially complex issues, start with the simple things and work your way up. Check obvious things, such as whether or not the boiler is turned on. If there are no lights whatsoever, then there may be no power going to the boiler. Check if your lights and plug sockets are working, and check the fuse box in case it has tripped. Also, check that your gas and water are working correctly. If you have a gas cooker, turn on the hob for a minute, and for the water, turn on your taps. If you are confident that the gas and water are working properly, you can move forward to the next step. 

Check The Boiler Controls Have Not Been Turned Off By Accident 

Some boilers have separate controls for the water and the heating. Many boilers are also located in an airing cupboard which inevitably becomes a storage area for towels and bedding. There is a chance that the water control on your boiler may have inadvertently been turned off, as towels were pushed into the cupboard. The simple flick of a switch could resolve your lack of hot water. 

Has The Timer Been Activated Accidently 

Depending on the type of boiler you have, the water heater may be on a timer. Perhaps the clocks have gone back or forward, the backup batteries may have failed, or the timer has just been set up wrong. Again this is a quick and easy fix if that is the source of the issue. 

Is Your Thermostat Working Properly?

Another potential reason for these types of issues could be the thermostat. If it is set to turn on or off at a specific temperature, then the reason you may not have any hot water is that that temperature has been reached, or the thermostat could have been accidentally set to off. Alternatively, if everything appears normal, there could be an issue with the thermostat itself, requiring a visit from a trained engineer. 

Check The Diverter Valve 

The diverter valve is a critical component of many boilers. The diverter valve is designed to alternate the heat between the heating system and the hot water. So if you have heat but no hot water or vice versa, your valve may not be operating properly. Unfortunately, this is not something you can resolve yourself and will require the services of a Gas Safe engineer.