Quick summary: A radiator staying cold after draining or refilling the system is usually caused by trapped air or uneven pressure rather than permanent damage. In most cases, it’s a circulation issue that settles once the system is correctly bled and balanced.
This tends to happen after boiler servicing, plumbing work, or any situation where the system has been partially drained. Once water is reintroduced, air can become trapped in places it wasn’t before.
Bleeding the radiator is usually the first step, but it doesn’t always solve the problem immediately. Sometimes air moves through the system gradually, meaning a radiator may need to be checked again after the heating has run for a while.
If bleeding doesn’t restore heat, the issue often lies in flow rather than air alone. Radiators further from the boiler can struggle to refill evenly if the system balance has shifted.
This overlaps with scenarios covered in radiators not heating after bleeding, where the fix is often less obvious than releasing air.
It’s also worth checking system pressure. Low or uneven pressure can prevent hot water from circulating properly, particularly after a refill.
In homes where multiple radiators are affected, uneven heating across the house gives more context.
For an overview of how small system adjustments affect overall warmth, this guide pulls the wider picture together.
