Radiator Leaking: Finding the Drip and Stopping It

What to do in the first ten minutes

Put a towel or a bowl under the drip and move anything that could be damaged, like rugs, furniture or electrical leads. If water is getting near a plug socket, switch that circuit off at the consumer unit.

Next, close both radiator valves. The control valve at one end turns by hand or with its thermostatic head set to zero or the snowflake. The lockshield at the other end hides under a plastic cap and needs a spanner. Count the turns as you close it so it can go back to the same setting later. With both shut, that radiator is isolated from the rest of the system and the drip should slow to a stop.

Where the water usually comes from

Dry everything off with kitchen roll, then watch to see where fresh water appears. A dry tissue wiped around each joint shows up the wet spot quickly.

• The valve spindle, just under the head or cap, where an old gland seal has worn
• The nut joining the valve to the radiator tail, or the joint into the pipe from the floor
• The bleed valve at the top, if it was not closed properly after bleeding
• A pinhole or rust patch on the radiator itself, often along the bottom seam

Leaks from valves and joints

Valve and joint leaks are the most common and usually the cheapest to sort. A loose nut can sometimes be nipped up a quarter turn, but go gently: overtightening an old brass fitting can crack it. A weeping spindle often needs a new gland or a new valve.

If the valve is old, stiff or the thermostatic head no longer works properly, swapping it is usually better than nursing it along. Our page on radiator valve replacement explains what that involves.

Leaks from the radiator body

Water coming through the metal itself is a different story. Radiators corrode from the inside, where sludge and oxygen in the water slowly eat into the steel. Once a pinhole appears, others tend to follow, and sealants are at best a short-term patch.

A corroding radiator is a sign there is sludge elsewhere in the system too, so it is worth asking about the condition of the water when the radiator is changed. We cover swapping old panels for new on our radiator installation page.

Check the boiler pressure

Any leak lets water out of a sealed system, so after a while the boiler pressure gauge will drop. If you have a combi or system boiler, check the gauge once the radiator is isolated. You may need to top it up before the heating will run properly again.

If pressure keeps falling after the radiator is isolated, there is another leak somewhere, perhaps under the floor or at the boiler, and that needs tracing by an engineer.

Need it sorted? Book a central heating visit

If the leak is from a valve, a joint or the radiator itself, we can repair or replace it and get the system back to pressure. Send a photo of the drip and the valve to 07429 632804 on WhatsApp, read more about our central heating work, or use the quote form and Chris will get back to you.