How to Fix / Troubleshooting

Safety first: Allow radiators to cool slightly before bleeding to avoid burns.

Steps to check:

Bleed all radiators starting from the lowest floor to the highest, topping up system pressure as needed.
Ensure all TRVs (thermostatic radiator valves) and lockshield valves are open.
Check that any external motorised zone valves near the boiler are opening when there is a call for heat.
Listen for the pump; if silent or excessively noisy, it may need replacement.
If some radiators remain cold at the bottom, a system flush by a professional is recommended.

Warning: Do not over-pressurise the system while bleeding. Monitor the gauge closely.

Boiler runs but radiators do not get hot or only partially heat

Possible Causes