Your heating is on, the boiler is running, but your house just isn't getting warm enough. Here are some quick checks you can do yourself:
DIY Checks You Can Do
Bleed your radiators – Feel each radiator. If they're cold at the top but warm at the bottom, use a radiator key to release trapped air until water comes out.
Check boiler pressure – Look at the pressure gauge on your boiler. It should read 1–1.5 bar when cold. If lower, you may need to repressurise using the filling loop.
Check your thermostat – Make sure it's set to heating mode and higher than the room temperature (18–20°C recommended).
Feel all radiators – Work out if it's one radiator, a few, or all of them that are cold. This helps diagnose the problem.
Can't Fix It Yourself?
Book a heating engineer on WhatsApp
We're Advanced Heating and Plumbing, covering North London, West London, Watford, Herts and Middx.
Our vans carry many common spare parts so we can usually get things working in the same visit.
Common Reasons Why Your Heating Isn't Warming the House
Air in Radiators
Air trapped in radiators stops hot water circulating properly. You might have hot pipes but cold radiators.
How to fix:
Use a radiator key. Turn the small valve anticlockwise until you hear hissing air. When water starts coming out, close the valve. Check boiler pressure afterwards.
System Pressure Too Low
Most boilers won't fire up properly if system pressure drops below 1 bar.
Check the pressure gauge – it should read 1–1.5 bar when cold.
If you need to repressurise frequently (more than once a month), you have a leak that needs fixing.
Thermostat in Wrong Location
If your thermostat is in a warm room or in direct sunlight, it may read warmer than the rest of your house. The boiler thinks the house is warm enough and doesn't fire up.
Check where your thermostat is located and what temperature it's set to.
Pump Not Working Properly
The circulation pump pushes hot water around your system. If it's failing, you might have a hot boiler but lukewarm radiators.
Signs of pump problems:
Boiler gets hot but radiators stay cold
Strange noises from the boiler
Only radiators nearest the boiler get hot
Sludge in the System
Over time, rust and debris accumulate in heating systems. This blocks pipes and radiators, preventing proper circulation.
Signs of sludge:
Radiators cold at the bottom
Boiler making gurgling or banging noises
Black or brown water when bleeding radiators
Sludge requires professional power flushing to remove.
Need Help Diagnosing the Problem?
Contact us on WhatsApp
We can often diagnose the problem over the phone and let you know if it needs a visit.
Call 0800 328 0449 nowWhen to Call a Heating Engineer
Boiler running but no heat – Likely pump failure.
Constant pressure loss – Indicates a leak.
Black water when bleeding – System needs flushing.
Multiple radiators cold – After bleeding and pressure checks.
Why Winter Makes These Problems Worse
During mild weather, you might not notice your heating isn't working at full capacity.
When temperatures drop significantly in winter, these issues become obvious because your boiler runs much longer and you need all radiators working properly.
Book Before Winter Arrives
September and October offer better engineer availability than winter.
You can book a convenient time and get problems fixed before cold weather arrives.
Booking a Heating Assessment is Easy with Us
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