How to stop a leaking radiator?

There’s nothing worse than having a leaky radiator and not knowing what to do. That’ll all about to change as we go over what you need to know to keep your home dry when you discover a leak…

The Basics of Finding a Leak

We know that the first thing that you’ll want to do is go all guns blazing to get the leak fixed, but before you can do anything you need to figure out where the leak actually is.


Put something on ground first to make sure to reduce the amount of water hitting your carpet or floor and causing lasting damage. The next thing is to dry the radiator off, this will make it much easier to actually find the source of the leak. While this is a generalisation, most radiator leaks come from 3 locations – the body of the radiator itself, the bleed point, valve or tail and the pipe filling the radiator with water. We’re going to look a bit deeper into a leaky valve or tail.

Radiator Tail

If you find a leak, the first thing that you need is to drain of your system. This will take out all of the water that is inside so that you can get to work on a fix for the leak. To do this, turn off your radiators supply valve, as well as undoing your lockshield valve.


At this point, we would recommend using a water pump plier that has a plastic jaw to undo the union nut. An adjustable spanner will do the same job but has the potential to mark up the chrome on fittings if it isn’t used carefully. Open the bleed valve from there. When you do this, you’ll notice that the dripping will still be happening but make sure that you have your towel at the ready to catch any water that comes out.


Once that’s done, use a good amount of PTFE tape and re-wrap the male end of the tail. It’s important to go too overboard with PTFE tape so we would recommend about 10-15 rotations. You’re almost there, so it’s time to re-tighten the union nut and open up the bleed and lockshield valves. Once the water is back in your radiator, take the time to re-check for any more leaks and close the bleed valve once you are happy.

Don’t Forget…

While this guide is aimed to help you take on a job, sometimes it’s best to call in the professionals and if you are not sure if you can do the job, recommend that you do. Water damage can be costly to repair so it’s always a good idea to get things sorted as quickly as possible.

Need an emergency plumber in the St Helens area?

If you are in need of an emergency plumber and are based in the St Helens area, don’t hesitate to pick up the phone and get in touch with us. We are always happy to help or answer any questions you might have!