Project Overview
| Location | Windlesham, Surrey (GU20) |
|---|---|
| Call-out | Emergency — radiators in the extension not heating up |
| System | Worcester Bosch gas boiler serving the house radiators and a vertical designer radiator in the extension |
| Fault found | Extension circuit not getting flow — radiator needed reconnecting, valves replacing, air clearing and the system balancing |
| Work completed | Circuit traced with an air test, new TRVs and lockshield valves, extension radiator reconnected, loft air vents fitted, system refilled and balanced |
The Challenge
A homeowner in Windlesham had radiators in their extension that were not working, while the rest of the house was heating as normal. It is one of the most common heating complaints after an extension is built: the new radiators sit at the far end of the circuit, the pipe routes are hidden under floors, and the water takes the easiest path back to the boiler through the radiators that were there first.
The job for our heating engineer was to find which pipes actually fed the extension, get its radiator connected and flowing, and leave the whole system balanced so the extension warms up alongside the rest of the house.
The Solution: Trace, Re-Valve, Vent and Balance
With the pipework hidden, we isolated the boiler and tested the pipework with an air compressor to identify the flow and return circuit serving the extension. Once the right pipes were confirmed, we fitted new thermostatic radiator valves (TRVs) and lockshield valves, and reconnected the extension radiator as the customer asked.
The system was then refilled and new air vents were installed in the loft, where trapped air collects at the high points of the pipe runs. Finally we used the lockshield valves to hold back the radiators in the rest of the house and balanced the system, so hot water was pushed out to the extension instead of short-cutting through the rooms nearest the boiler.
Why Extension Radiators Go Cold
A heating system does not share hot water out evenly on its own. Water follows the path of least resistance, so radiators close to the boiler get most of the flow and anything added at the end of the circuit is left with what is left over. This Windlesham job hit the usual causes:
- Unknown pipe routes: Extension pipework is often teed in under floors. An air test identifies the flow and return without lifting floorboards on a guess.
- Tired or missing valves: New TRVs control each room’s temperature, and new lockshield valves give the engineer a reliable way to set how much water each radiator takes.
- Trapped air: Air gathers at high points, often in the loft, and can stop a long pipe run circulating. Automatic air vents let it escape so the extension circuit keeps flowing.
- An unbalanced system: Closing down the lockshields on the radiators nearest the boiler and opening up the far ones is what finally sends heat to the extension.
The Repair Process
- Isolate and trace: The boiler was isolated and the pipework tested with an air compressor to identify the extension’s flow and return.
- New valves: New TRVs and lockshield valves were fitted, and the extension radiator was reconnected as the customer requested.
- Refill and vent: The system was refilled and new air vents were installed in the loft to clear trapped air.
- Balance: Radiators in the rest of the house were held back on their lockshield valves and the system was balanced.
- Prove it: With the boiler running, the extension radiators were confirmed getting warm before we left.
The Results
The boiler is running and the extension radiators are getting warm. The Windlesham extension is now part of a balanced heating system rather than an afterthought at the end of the pipe run, with new valves that let each room be controlled properly.
Recommended Follow-Up
- 28mm pipework at the boiler: Increasing the pipework by the boiler to 28mm would improve flow rates now that the system is feeding an extension as well as the original house.
- More valve changes: A few of the other radiators would benefit from new valves at some point.
- Boiler service: The Worcester Bosch is due a boiler service, which is a good time to check system pressure and flow.
Cold Radiator Questions
Why are the radiators in my extension cold when the rest of the house is warm?
Usually because the system is not balanced, the extension pipework has air in it, or the valves are not letting water through. Hot water takes the easiest route, so radiators nearest the boiler hog the flow unless their lockshield valves are set to share it.
What does balancing a heating system involve?
An engineer adjusts the lockshield valve on each radiator so they all heat up evenly — closing down the ones nearest the boiler and opening up the ones furthest away, then checking the temperature of the flow and return pipes.
Do you cover Windlesham?
Yes. Talis covers Windlesham and nearby Camberley, Ascot, Wentworth and Virginia Water for plumbing and heating repairs. For another heating circuit fault, see our Hive and zone valve repair in Virginia Water.