Hot Water But No Heating?
Here's What Might Be Causing It
If you’ve got hot water but no heating, you’re not alone this is one of the most common problems homeowners face, especially as temperatures start to drop. Everything seems fine when you turn on the tap, but the radiators stay cold, and your home feels like a freezer.
It can be a confusing issue. After all, if the boiler’s giving you hot water, shouldn’t it be working for the heating too?
Let’s break down the most likely reasons for this problem, what you can do to check for simple faults and most importantly why it’s essential to get a professional involved if the issue isn’t a quick fix.
Why You Have Hot Water But No Heating
1. Faulty Room Thermostat
This might sound obvious, but it’s one of the first things to check. If your room thermostat isn’t set correctly or isn’t working at all it could be telling your boiler not to heat the house.
What to check:
Make sure the temperature is set above the current room temperature.
Try increasing the thermostat setting and listen for a click or check if the boiler responds.
If your thermostat runs on batteries, check if they need replacing.
2. Programmer or Timer Issues
Your heating system might simply not be scheduled to turn on. A faulty programmer or a misconfigured timer can result in heating not kicking in, even when everything else seems fine.
What to do:
Check the settings on your boiler or wall programmer.
Make sure the heating is not set to “off” or limited to certain times that don’t match when you’re checking.
Sometimes the clocks go out of sync, especially after power cuts or daylight saving time changes.
3. Airlocks or Trapped Air in the System
If you’ve got hot water but radiators aren’t heating up, there might be air trapped inside them, stopping hot water from circulating properly.
What to look for:
Radiators cold at the top but warm at the bottom
Gurgling or bubbling noises
You can bleed a radiator using a radiator key to release the trapped air. Just be careful this can get messy, and the system may need repressurising afterward.
4. Low Boiler Pressure
Your boiler needs the right pressure to push hot water around the radiators. If the pressure drops too low, your heating won’t function, even though hot water from taps might still work.
What to check:
Look at the pressure gauge on your boiler ideal pressure is usually between 1.0 and 1.5 bar.
If it’s below that, the system may need topping up using the filling loop (usually a silver flexible hose beneath the boiler).
Important: Only top up the pressure if you know how to do it safely. Overfilling or incorrectly operating the filling loop can damage the boiler or cause leaks. We suggest to call a professional.
5. Stuck or Broken Diverter Valve (Combi Boilers)
If you have a combi boiler, a part called the diverter valve controls where the heat goes either to your taps or to your radiators. If it gets stuck on the hot water side, you’ll get hot water but no heating.
This is a very common failure and not something you should attempt to fix yourself. It requires a qualified heating engineer to diagnose and repair.
6. Pump Failure
The circulation pump is responsible for moving hot water from the boiler into your radiators. If the pump fails or is jammed, the water won’t circulate, and the radiators will remain cold even if the boiler is producing heat.
Signs of pump issues include:
A noisy boiler
Radiators that stay cold even when the boiler is running
No difference when you increase thermostat settings
Again, pump repair or replacement should always be done by a professional.
Why It’s Best to Call in the Experts
It’s tempting to poke around your boiler and heating system when things go wrong, especially if you’re handy around the house. But here’s the truth: modern boilers are complex and potentially dangerous systems that require expertise to service correctly.
Incorrectly adjusting pressure, tampering with internal valves, or attempting DIY repairs can:
Void your boiler’s warranty
Cause leaks or even damage the boiler permanently
Risk gas leaks or carbon monoxide exposure
If basic checks (like your thermostat or pressure gauge) don’t reveal the issue, it’s time to call in a Gas Safe registered heating engineer.
When you’re getting hot water but no heating, it’s usually a sign that your boiler is trying its best but something’s not quite right in the system. From thermostats to valves and pumps, there are several possible causes.
Do the simple checks first, but don’t hesitate to get professional help if needed. Your comfort and safety are worth it.
Book a Heating Engineer Today
If you’ve got hot water but no heating, don’t suffer through chilly mornings or freezing nights. A professional heating engineer can quickly identify and fix the issue safely and efficiently.
Whether it’s a diverter valve fault, trapped air, or a pump problem, we’re here to help. With years of experience and fully qualified engineers, we’ll get your heating back up and running in no time.
