Central Heating is not working but hot water is. Here’s What You Need to Know

Are your radiators cold but your taps producing hot water? You’re likely wondering, “Why is central heating not working, but hot water is?”

This common issue typically stems from incorrect boiler settings, radiator airlocks, or a faulty diverter valve. If your radiators aren’t working but hot water is, this guide will walk you through how to identify and fix the problem safely.

Step-by-Step Guide: What to Do When Hot Water Works but Central Heating Doesn’t

1. Start with the Radiators

Check all the radiators in your home:

• Are all the radiators cold? This usually points to a system-wide issue, like the boiler not heating water for central heating.
• One or two radiators warm or slightly hot? This could be trapped air or sludge buildup, not a boiler fault.

Try This:

Bleed the Radiators:

• Turn off the heating.
• Use a radiator key to slightly loosen the bleed valve (turn anti-clockwise).
• Wait for the air to escape, once water drips, tighten it back.
• Use a towel or container underneath to avoid a mess.

Read our blog on how to bleed your radiators for a more detailed guide.

Still cold at the bottom but warm at the top?

• This often means sludge buildup inside the radiator.
• In this case, you may need a professional radiator flush or cleaning service.

Related Article: What is a central heating power flush?

2. Check Thermostat and Timer Settings

It may sound basic, but there is a lot of hot water on, but no heating issues are due to incorrect settings.

What to Check:

• Thermostat: Is it set high enough to trigger the heating?
• Programmer or Timer: Is it set to “heating on”? A power cut or daylight saving change may have reset your settings.
• Room Thermostat: Ensure the target temperature isn’t too low.

Even if your hot water is working but the central heating isn’t, it doesn’t mean your boiler is faulty; your controls might need adjusting.

Related Article: How does a thermostat work?

3. Check Boiler Pressure

Boilers rely on water pressure to circulate hot water through the radiators. Low pressure could be the reason if your hot water is working but not heating your home.

How to Check:

• Look at the pressure gauge on your boiler.
• If it’s below 1 bar, you must repressurise the boiler (consult your user manual).

Warning: Do not open any casing. Use only accessible controls and refer to your boiler’s instruction manual.

4. Reset the Boiler

If there’s a minor fault in the system, resetting the boiler might fix it.

To Reset:

• Use the reset button on your boiler’s control panel.
• Alternatively, turn the boiler off at the mains, wait 30 seconds, and turn it back on.

Note: If the issue returns after resetting, the fault may be deeper, often related to a component failure.

5. Could It Be the Diverter Valve?

If hot water is flowing but radiators aren’t heating, and you’ve tried all of the above, your motorised diverter valve may be stuck or broken.

This valve decides where the boiler sends hot water, to the taps or the radiators. When it fails:

• You’ll usually get hot water but no heating.
• It’s a mechanical part that wears out over time, especially in combi boilers.

This is not a DIY fix. Only a qualified Gas Safe registered engineer should replace or repair a diverter valve.

Quick Troubleshooting Summary

Safety First: Don’t Risk a DIY Disaster

Did you know? If you’re not certified, tampering with a gas appliance is illegal and unsafe. If you’re not sure what to do:

Call 24|7 Home Rescue on 0345 3192 247

Our friendly technical team will help you by booking your appointment with a Gas Safe registered engineer to fix your heating system professionally.

Central Heating System

Keep your home warm and energy-efficient with our one-off central heating system servicing. Extend the life of your system, reduce energy bills, and avoid unexpected issues.

Buy Central Heating!

Still Having Trouble?

You shouldn’t have to deal with cold radiators and chilly nights. Our team is here to help you with reliable and affordable boiler repair service, and once you’re covered with us, you won’t need to worry about these issues again.

24|7 Home Rescue covers:

• Central heating repairs
• Boiler breakdown cover
• Annual boiler services
• CP12 Certificate
• Landlord Cover

Conclusion

If your central heating is not working but your hot water is, don’t panic. Follow the steps above, and the issue can often be resolved without a costly repair. Still, if the problem lies in the diverter valve or another internal component, it’s time to call in the pros.