Radiators that don't heat up fully, develop cold spots, or start leaking are a common problem in Bristol's older central heating systems. Cold patches at the top of a radiator typically indicate trapped air that can be resolved by bleeding. Cold patches at the bottom or across the whole radiator usually point to sludge accumulation — a mixture of corroded iron particles and magnetite that settles at the lowest point of the radiator and reduces flow. This is particularly common in older systems that haven't been maintained with inhibitor. Our plumbers bleed, flush, and balance radiators and, where a radiator is damaged or severely corroded, can supply and fit a replacement. We also check and repack leaking radiator valves, replace thermostatic radiator valves (TRVs), and balance the system so all radiators reach temperature evenly.
We identify whether the issue is trapped air, sludge accumulation, a faulty valve, or a damaged radiator body.
Where trapped air is the cause, we bleed the radiator at the bleed valve and re-pressurise the system to the correct level.
Leaking or seized lockshield and TRV valves are repacked, repaired, or replaced.
For sludge-affected radiators we isolate, remove, and flush the radiator externally before refitting.
We balance the system so all radiators heat evenly, adjusting lockshield valves to optimise flow distribution.
Radiator bleeding from £55. TRV or lockshield valve replacement from £85 per radiator. Radiator removal, flush, and refit from £110. New radiator supply and installation from £180 including labour.
Turn the heating on, let it reach temperature, then switch it off. Use a radiator key to slowly open the bleed valve until air hisses out and water follows — then close. Check system pressure on the boiler afterwards.
Recurring air in the system suggests a leak allowing air ingress, a faulty auto air vent, or an issue with the expansion vessel. We can diagnose the root cause.
Pinhole leaks in radiator bodies are rarely cost-effective to repair permanently. A replacement radiator of the same output can usually be fitted in under two hours.