How to Fix a Leaking Radiator

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Last updated: October 31, 2023

Leaking radiators are more common than you might think. While your first inclination might be to call the plumber straight away, this can be a costly endeavour. Before reaching out to the professionals, it might be well worth it to learn how to fix a leaking radiator. The number one tell-tale sign that you are dealing with a leaky radiator is coming home to find a wet patch on the floor. However, do not despair. Once you have figured out the source of the leak and got a few tools at your disposal, you should be able to fix it in a jiffy. If you want to learn the ins and outs of fixing a leaking radiator or a radiator valve or joint, then it is time to read on and learn about the different leaks that might occur and how best to fix them.

While you’re figuring out how exactly to fix it, you might want to pop some towels or a bucket below your radiator. This will protect your floor (especially if you have a wooden floor or carpet) and surrounding furniture. Water damage can be pretty expensive, so you want to ensure that no further damage occurs.

How to Identify Where it’s Leaking From on Your Radiator

If you notice a wet patch beneath your radiator, then sure as day, you have a leak. The first step in fixing your leaking heating system is to identify where the leak is coming from. Once you have identified the source of the leak, you can determine what part of the radiator you need to fix.

The first step is to dry your radiator with an old towel completely. When your radiator is completely dry, you will easily be able to see where the leak is coming from. For extra ease, use some kitchen towel or loo roll and run it across the radiator’s different valves, fixtures, and parts. You will soon see where the leak is coming from, and you can get to work and fix the radiator leak.

Drain Your Radiator

Before fixing the leak, you will need to drain your radiators of water. You’ll want to switch your central heating system off and ensure that it cools down as you do not want to risk getting burnt with hot water. This is a simple job and requires you to:

  1. Switch off your boiler system
  2. Turn off the water valve on your radiator.
  3. Find the drain-off valve of your central heating system, and connect a hosepipe to it, ensuring that one end can reach outside (because you don’t need more water spilling on the floor!)
  4. Open the valves of the radiator you want to fix and open up the specialised ‘bleed valves’ for a quicker drain. This will get your radiator to the bleed point and ensure that all of the water has drained. You’ll need a dry system before you try and fix the leak.
  5. Once all the water has drained, close the valves again, and unplug the hosepipe.

if it feels a little complex, you can check out several online tutorials that will show you how to do this first step effectively.

Tools Needed for Fixing a Leaky Radiator

  • An adjustable spanner
  • PTFE tape
  • Buckets and towels
  • Hosepipe

Leaking Radiator Valve

If you notice that the leaking is terminating from the radiator valve, you’re in luck (sort of) as it is a pretty easy leak to fix. Over time, the various components within the radiator valve, such as the spindle packing located inside, can break down due to wear and tear. This is normal because the radiator valve sees the most human interaction of all the components.

To fix a leaking valve, you need to:

  • Turn both valves off (the supply valve and the lockshield valve)
  • Using the adjustable spanner, loosen the union nut (located between the radiator and the feeder pipe). Take note of how many turns this takes.
  • Turn off the bleeder valve, and pop a towel under the radiator in case there is any excess water.
  • Wrap the specialised PTFE tape around the valve between ten and 15 times until secure
  • Once secure, tighten the union nut with your adjustable spanner with the same number of turns you took to loosen it.
  • Once the water is in the system, be sure to close the bleed valve and double-check for any more leaks.

If your valve has seen better days, you will need to purchase a replacement valve to replace your existing valve. Be sure to jot down the model name and take a picture before heading to the hardware store, as this will ensure you buy the correct fitting. Sometimes the body of the valve breaks down over time, and in this case, a new valve is advisable. Depending on the type of radiator valves you need, this won’t necessarily be a costly buy. If you have a smart radiator system, however, you might have to fork out a bit extra.

Water leak through the heating radiator

Leaking From the Radiator Spindle

Luckily, a radiator spindle leak is also a pretty easy problem to fix. Usually, you will just need to use your adjustable spanner to tighten the gland nut. The gland nut is located just above the rising spindle of a manual control valve. Tightening it should do the trick; however, if the leak persists, you will need to unscrew the gland nut and wrap some PFTE tape around the spindle to ensure that it is completely secure.

Leaking From the Radiator Gland

If you have fixed the valve, but there is still water leaking, you might, in fact, have a radiator leak from the radiator gland.

  • Firstly, close the valve, and if there is remaining water or the leak persists, and you notice some water coming from the plastic cap, then you will need to turn off the lockshield valve too.
  • Once the plastic cap has been removed, you will need to loosen the gland nut until it unscrews.
  • You’ll then need to take your PFTE tape (about 20 cm) and wrap it around the spindle valve.
  • Once the tape is securely around the spindle valve, secure the gland nut once again.

Leaking From the Radiator Pipe Joint

Compression heating systems utilise radiator pipe joints; however, with general wear and tear, they can become loose over time and cause leaks. if you need to fix a radiator pipe joint, you will have to do the following:

  • As always, make sure that your radiator is fully drained well below the point where the leak is occurring.
  • using your spanner, unscrew the nut from the radiator pipe that is leaking
  • Securely wrap the PFTE around the point where the compression fittings (known as olives) meet the joint.
  • Tighten the nut securely, and your leak should be fixed!

Leaking From the Radiator Body

Sometimes leaks are caused by corrosion. Like all household appliances and products, radiators can get old over time, and a build-up of sludge can cause the radiator to deteriorate over time. Usually, these leaks – also known as pinhole leaks – are a sign that the end is near. While you can temporarily fix them with a plastic sealant, however, this is not a permanent solution and will only buy you a bit of time.

Check out our latest article on: Best Bathroom Sealant

Leak Sealers

Leak sealers are a fantastic idea for small, annoying persistent radiator leaks and might buy you some extra time. They are often used for weeping joints or for parts of the radiator that are hard to reach. These sealers work best when warm water is circulating and should be able to offer respite within about 24 hours. However, if an actual fitting needs changing (like a radiator valve) needs replacing, you will want to do this first.

Preventative and Protective Measures

Leaking water can cause pretty severe damage to furniture and floors and should be taken seriously. While many smaller jobs are manageable at home, sometimes you’ll need to consult the experts if you are faced with a tricky job. A leaking pipe is one thing, but a replacement radiator might be the only option if you need an entirely new heating system.


Depending on what part of your radiator is leaking, it can be a simple job or a pretty tricky one. If corrosion has occurred, you will need to replace your radiator eventually. This can be pretty costly and should be done sooner rather than later if possible. While some repair jobs, like a leaky radiator valve or water pipe, can be fixed at home, some jobs need an experienced plumber. If you’re feeling unsure, then it’s always best to consult professionals.

While replacing a radiator valve or a spindle might seem frustrating, it is a much cheaper solution than having to replace your whole radiator. Added to this, if you notice small patches of rust and corrosion, but a radiator leak has not yet occurred, it might be worth fixing it before problems arise. A little maintenance can really go a long way in ensuring optimum radiator health.

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