Radiators heat unevenly; some remain cold while others are hot.

Safety first: Radiators and pipes can be hot. Use a cloth when bleeding valves.

• Bleed radiators: Starting with the highest and furthest radiators, bleed air until water flows steadily.
• Balance system: Adjust lockshield valves on the hottest radiators to reduce flow slightly, forcing more flow to cooler radiators. Make small adjustments and allow time to stabilise.
• Increase pump speed: If the pump has adjustable speed, try a higher setting to improve circulation.
• Consider flushing: If some radiators remain cold at the bottom, sludge may be present. A chemical or power flush may be required.