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Why is my boiler giving me hot water but no heating?

In this handy guide, we will give you some tips on what you should look out for to determine the cause of the issue and to help you get your central heating back up and running effectively.

Check the central heating settings on your boiler

We rarely give our boilers much thought when they are running and supplying our homes with hot water and heating. If you have noticed that your boiler is providing you with hot water but no central heating, it can be frustrating and potentially confusing. Sometimes this can simply be down to having the controls of your central heating system set on the incorrect settings. However, it can also be down to faults within the system itself.

Check the central heating settings on your boiler

The first step you should take to determine the issue is to inspect the settings on your boiler interface to ensure your heating settings are switched on and set correctly. Using the display on your boiler, check to see whether your central heating is turned on and is not currently being controlled by a timer.

Once you have inspected these, you should check that the flow temperature of your boiler is set to between 60 and 70°C. This will ensure the water is warm enough when it reaches your radiators. If the flow temperature is too low, the water will not be warm enough to adequately heat your radiators.

Check the radiators and thermostatic valves

The next step you should take is to check all of the radiators in your home to rule out if it is an issue with your central heating or a single radiator. This also includes checking any thermostatic valves to ensure they are turned up to an adequate temperature.

If you notice some of your radiators are warm with cold spots, this is an indication that there is trapped air within the system. If this is the case, we would recommend following these steps to bleed your radiators to release the trapped air.

Check the room or wireless thermostat

If you have inspected the settings on the boiler itself but you are still experiencing issues with the central heating, you should check the room thermostat. There are lots of different types of room thermostats so this will vary depending on the type you have.

If you have a traditional, mechanical thermostat, you should check to see whether the dial is turned up. Setting your thermostat to between 18 and 21ºC should adequately heat your home to a comfortable temperature. If this is switched on and the settings on your boiler are correct but your central heating is still not working, this could indicate a fault with the thermostat.

Like traditional thermostats, wireless thermostats are best placed in an area of your home where there is a balanced temperature. This should be a room near the centre of your home away from direct sunlight and drafts from windows or doors. If it is currently in a position where it could be affected by extreme temperatures, you should try repositioning it, ensuring it still has a good connection to the boiler. Failing that, you should check to inspect the device to see if the batteries need changing. This is usually indicated by a low battery symbol on the device.

Check the boiler pressure

Every boiler requires adequate pressure within the system to allow it to function correctly and keep water circulating in the heating system. As a general rule of thumb, this should usually be between 1 and 2 bars when the heating is on, but it can drop to between 1 and 1.5 when the heating is off. We would always recommend referring to your boiler manual to see the pressure for your specific model.

You can check the boiler pressure by inspecting the pressure gauge. This is usually a round dial on the front of your boiler. If you find the boiler pressure is too high, this can often be resolved by bleeding your radiators. By doing this, you’ll remove any trapped air pockets within the system allowing the water to circulate freely.

If you find that the boiler pressure is low, this can be fixed by adding more water to the system to repressurise it. Every boiler is different so the steps you need to take to do this will vary. We would highly recommend checking the manual for specific instructions for your boiler.

A general guide on how to repressurise a boiler:


Whilst low boiler pressure is not dangerous, it could be a sign of a fault within the system such as a small leak. If you are in any doubt about how to repressurise your boiler or are concerned there might be a fault, we would recommend contacting your local Glow-worm installer.


My combi boiler is giving me hot water but no heating

If you have a combi boiler and you have completed the above steps but are still finding your heating is not working, it could be an issue with the diverter valve.

The diverter valve in your combi boiler is responsible for directing hot water to either your radiators or taps and showers. This valve prioritises the flow of water depending on what is being used. For example, if the heating is on, but someone turns on a hot tap, the valve will prioritise sending hot water to the tap rather than the radiators. However, if all the hot water taps in your home are turned off and you are still not getting central heating, this could indicate that the diverter valve is stuck or faulty. In this case, we would recommend contacting your local installer who will be able to investigate this for you.


If you still have no heating, contact your local installer

If you have tried the solutions above but you are still experiencing issues, we would recommend contacting your local installer who will be able to diagnose the problem for you.