Where a radiator is cold tells you most of what is wrong with it. Tell us which radiators are misbehaving and what you have already tried, and we will look for an available local plumber covering your area.
A radiator cold at the top and warm at the bottom has air trapped in it, and bleeding it usually fixes that in a couple of minutes. A radiator that is warm at the top and cold along the bottom is the opposite problem: sludge and corrosion debris have settled in the base and water is no longer circulating through it. That needs flushing rather than bleeding.
One radiator cold while the rest of the house is fine normally points at its valves — a thermostatic valve with a pin stuck down, a lockshield closed too far, or a valve that has seized after a summer of sitting still. Radiators at the far end of the system heating up last, or barely at all, is a balancing problem: the nearest radiators are taking most of the flow and the run needs adjusting.
If every radiator is cold, the problem is usually not the radiators at all — it is the boiler, the pump, a motorised valve, the thermostat or the system pressure. Say so in your enquiry, because it changes who the job needs to go to.
Bleeding a radiator is one of the few heating jobs that is genuinely a household task. Turn the heating off and let the system cool, hold a cloth under the bleed valve at the top of the radiator, and open it a quarter turn with a bleed key until the hissing stops and water appears. Close it before more than a trickle comes out.
Repeated pressure loss, or a system that needs topping up often, usually means a leak somewhere and is worth investigating rather than repeatedly refilling.
Sludge is the most common underlying cause of radiators that never quite work. It is black iron oxide formed inside the system over years, and it settles in the bottom of radiators and clogs the pump and valves. A chemical flush or a power flush, followed by an inhibitor, is the usual remedy — but it is a system job rather than a radiator job, and on an older system a plumber will want to look at the whole thing before recommending it.
Boiler repairs and any work involving gas must only be completed by an appropriately Gas Safe-registered engineer. A plumber can work on radiators, valves and heating pipework; they cannot open up a gas boiler unless they hold that registration. Describe the symptoms as you see them and the enquiry can be pointed at the right trade.
Vofix is a matching service that connects customers with independent local plumbers. The plumber will confirm availability, pricing and the scope of work directly with you before work begins.
Availability varies by area and by day, so attendance is always subject to plumber availability. Vofix does not set or control the prices plumbers charge.
Three steps from telling us about the job to speaking with a local plumber directly.
Share a few quick details about your plumbing job, big or small.
We look for a plumber in the Vofix network covering your area.
Speak directly with your plumber and get the job sorted.
That is the signature of sludge and debris settling in the base of the radiator, which stops water circulating through the lower half. Bleeding will not help — it needs flushing, and if several radiators are the same the whole system probably needs attention.
Occasionally, and typically at the start of the heating season. If you are bleeding the same radiator every few weeks, air is getting in somewhere — often a small leak or a failing automatic air vent — and that is worth looking at properly.
Usually yes, provided the pipework can be re-run. It is a bigger job than a straight swap because it involves draining the system and altering pipes, sometimes under a floor, so get it priced before committing.
Not for the radiator itself. Radiators, valves and heating pipework are plumbing work. Anything involving the boiler or gas — including opening up the appliance — must only be completed by an appropriately Gas Safe-registered engineer.
Central heating: what needs Gas Safe cover →A like-for-like replacement typically falls within a guide range of around £150–£300 in the Midlands, supplied and fitted, with larger radiators and repositioning costing more. Vofix does not set prices — the plumber confirms the cost with you first.
See the full price guide →Tell us which radiators are affected and what you have tried, and we will look for an available local plumber. Free to use, with no obligation.
Heating and pipework pages that go with this one.