No Heating But Still Have Hot Water? Here’s What Could Be Going On

It’s a cold day in London, you’ve got hot water in the taps—but the radiators are stone cold. Sound familiar? You’re not alone. At Pleasant Plumbers, this is one of the most common heating-related issues we’re called out to diagnose.

Modern boilers are more reliable than ever, but problems can still arise. And when your system is delivering hot water but failing to heat your home, it can be tricky to figure out what’s wrong without calling in a professional heating engineer in London.

Here’s a breakdown of the possible causes, what to check yourself, and when it’s time to call a Gas Safe registered plumber.

Yes, and in many systems—it’s by design.

If you’ve got a combi boiler, it heats water on demand and can prioritise hot water delivery without activating your central heating. You may simply have it set to hot water only, especially if your thermostat or boiler controls were adjusted during warmer months.

In traditional systems with a hot water cylinder, an immersion heater (which uses electricity) may be operating independently of your boiler. So yes, hot water without heating is entirely possible—whether by choice or by fault.

Before you call a plumber in London, check these quick fixes:

• Your Boiler Settings: Make sure your boiler is set to heat both hot water and radiators—not just water.
• Thermostat Issues: If your room thermostat is set too low, your heating won't kick in. Try turning it up past 20°C.
• Timer/Programmer: Has your heating schedule changed? Double-check for daylight savings or power cuts that may have reset your system.
• Radiator Valves: Some homes have thermostatic radiator valves that may have been turned down. Make sure they’re open.

If everything above checks out and your radiators are still cold, it could be a mechanical fault. Common culprits include:

• Air Trapped in Radiators: If your radiators are warm at the bottom but cold at the top, they may need bleeding.
• Sludge Build-up: Over time, sludge can block the system, reducing heating performance. A system flush might be needed.
• Faulty Diverter Valve: In combi boilers, the diverter valve directs heat either to taps or radiators. If it’s stuck, you’ll get hot water but no heating.
• Ignition or Burner Issues: A misfiring boiler may still produce hot water but struggle to maintain consistent heating.

Only a Gas Safe engineer should open and diagnose these internal components. If you’re in Central London or the surrounding areas, our heating engineers in London can get to you fast.

Boilers typically last 10–15 years. If your system is frequently breaking down or your parts are no longer supported by manufacturers, it might be more cost-effective to replace it entirely. A new boiler could also improve your EPC rating, reduce your bills, and come with a longer warranty.

Not sure what to do? One of our Gas Safe engineers will assess your boiler and give you an honest breakdown of your options—no pushy sales pitch.

At Pleasant Plumbers, we understand how frustrating it is to have heating issues in the middle of winter. Whether you need a quick fix, a full system flush, or a brand-new boiler, we’ll handle it professionally, efficiently, and with minimal disruption to your day.

📍 Based in London
📞 Call or WhatsApp us on 0800 046 1000
📅 Or book your appointment online

No heat? No problem. Let Pleasant Plumbers bring the warmth back.