Radiators heat unevenly; some are hot, others remain cold or only warm at the top.

Safety: Allow radiators to cool slightly before bleeding to avoid scalding.

Steps:

• Use a radiator key to bleed air from the top of each radiator until water flows steadily.
• Check system pressure afterwards and top up if needed.
• If some radiators remain cold, their lockshield valves may need balancing (adjusting flow) or the system may require flushing.

System balancing and powerflushing are best carried out by a heating engineer.