We understand the frustration when your hot water is running fine, yet your radiators are cold to the touch. Especially when it’s one of those cold winter nights, and you’re having to rely on hot water bottles to make sure you’re not freezing!
No need to panic, because this issue is more common than you might think, and there are several reasons your heating might be having issues. In this guide, we’ll cover all the reasons why you have hot water but no heating, and how to fix them.
Reasons for no heating but hot water
There’s no single reason why your heating is having trouble, but your hot water is fine. Instead, there are several reasons this might be the case, and half of the job is figuring out what it is. We’ve given some of the most common reasons below:
Stuck diverter valve
The diverter valve controls the flow of water between the hot water and the heating, and a stuck diverter valve is one of the most common reasons why your hot water is fine, yet there’s no heating.
Essentially, the diverter’s internal mechanism has likely become blocked by debris or sludge from the system, causing it to stick and preventing the hot water and heating systems from operating freely.
Either that, or the motor that actually moves the valve has burned out.
So, what’s the fix? Well, in this case, you’ll need to get a Gas Safe-registered engineer to take a look, as it’s illegal for anyone else to operate or perform any maintenance on a gas boiler.
Not only are you breaking UK laws, but you’re also putting yourself at risk, as tampering with a boiler that you don’t know how to fix can lead to gas leaks and carbon monoxide poisoning.
By getting your boiler repaired by a registered engineer, you can ensure your own safety and that of everyone around you.
Low boiler pressure
Another common reason your hot water is fine yet there’s no heating is low boiler pressure.
This is usually caused by the water pressure in the system dropping below its ideal level. Most combi boilers have a pressure gauge, usually on the front of the boiler, that displays the current pressure in “bar”.
For the ideal pressure, you should see the boiler dial set between 1 and 2 bar.
If you’re seeing the dial too low, you can increase the pressure yourself by using the boiler’s filling loop, a flexible hose that lets you add a small amount of mains water to the boiler.
One thing to keep in mind is that if you’re regularly adding water to the boiler, you’ll likely have a leak in the system that should be addressed by a professional.
Learn more: Why does my boiler pressure keep dropping?
Faulty thermostat or controls
The issue might not be with the boiler itself, but with the thermostat or controls. Your thermostat is responsible for your central heating system, and has nothing to do with your hot water, so as simple as it sounds, it’s worth checking to see if the issue lies here.
It really could be something that’s incredibly simple – like the batteries being dead, especially if you’re using a digital or wireless thermostat.
Temperature settings might also be the issue. If your room temperature is currently 18°C, but your thermostat is set to 16°C, the boiler won’t turn on because it’s not needed.
And possibly the simplest of all, check it’s on. It really does sound incredibly obvious, but it’s easy to overlook.
If you’ve checked all of the above and you’re still having issues, it’s probably time to give a professional a call, as it might be something more serious, like a communication fault between the boiler and the thermostat.
What should you do before calling a professional?
We’ve covered some of the most common reasons and how to fix them – if you can – but what else can you check before calling a professional?
It’s important to remember that safety comes first, so the solutions listed below are all things you can do yourself, but if you’re not sure, it’s always best to call a Gas Safe-registered engineer.
Perform a system reset
The simple turn-off and turn-on approach. Sounds simple, but if your boiler has encountered an electronic glitch that’s disrupting the heating, a simple reset might be all that’s needed.
Bleed your radiators
This is something you can do yourself, but if you’re not sure or don’t feel like you have the skill or DIY experience, it’s best to call a professional.
The bleed process involves opening the bleed valve on each radiator to allow water to escape. You’ll need a radiator key, which is a specific tool designed to fit your valve. Sometimes, you can use a flathead screwdriver, but that depends on the valve itself. It can be a messy process, but it’s worth it if you’re having issues with your radiators.
Learn more: How to bleed a radiator (video)
When is the right time to call a professional?
Some issues can only be fixed by a Gas Safe-registered engineer, and it’s best to leave them to the professionals.
It’s not worth putting yourself at risk with legal and safety concerns. If you’ve checked all of the DIY solutions we’ve mentioned and you’re still having issues, give a professional a call.
