How to Fix a Leaking Radiator Valve: Complete Guide

Last updated on October 5th, 2023

Most radiator leaks come from a radiator valve.

If your radiator is leaking water from the panel, then you will most likely need to replace the radiator.

Knowing how to fix a leaking radiator valve will help you save money but you might need to replace it.

I have been fitting and fixing radiators full-time for over a decade and have learned a lot along the way.

Here I’ll show you how to fix a leaking radiator valve from my on-the-job experiences.

Where is the Radiator Valve Leaking From?

Leaking Radiator Valve Nut

A leaking radiator valve nut is the most common and easiest leak to fix on a central heating system.

There are three nuts on most radiator valves:

• The side nut connecting the valve to the radiator
• The bottom nut connecting the valve to the heating system
• The packing gland nut on the top of the valve

A radiator valve leak can come from any nut.

The simplest solution to fix a leaking radiator valve nut is to tighten the nut (clockwise) with an adjustable spanner.

If this doesn’t work, you should add some plumbing jointing compound to the threads on the leaking nut.

Here’s how:

1. Drain the heating system
2. Turn the leaking radiator valve nut anti-clockwise with an adjustable spanner until it comes away from the valve
3. Add lots of plumbing jointing compound around the threads
4. Tighten the nut back onto the radiator valve
5. Clean all the excess plumbing jointing compound off the valve
6. Refill the system and check for leaks

Leaking Radiator Valve Gland

A leaking lockshield valve can be fixed quite easily when it is leaking from the packing gland on the top of the valve.

The gland nut can be tightened (turned clockwise) with an adjustable spanner. This will fix almost all leaks from the gland.

If the leaking lockshield valve continues to leak after tightening it, then you can try wrapping some PTFE tape around the threads.

Here’s how:

1. Drain the central heating system
2. Remove the packing gland with an adjustable spanner
3. Wrap some PTFE tape around the threads
4. Refit the gland in the leaking radiator valve
5. Refill the system
6. Check for leaks

Leaking Thermostatic Radiator Valve

If you have a leaking thermostatic radiator valve (TRV), and it’s coming from the pin at the top of the valve, then you will probably have to replace the full valve.

Sometimes you can replace the leaking thermostatic radiator valve gland seal on certain valves (Danfoss and Drayton do some) but you’re better off replacing the valve.

If the leak is coming from around the brass nut gland that the pin is in, then you can try tightening it with an adjustable spanner by turning it clockwise.

Failing that you can try adding some PTFE tape to the threads:

1. Drain the central heating system
2. Remove the packing gland with an adjustable spanner
3. Wrap some PTFE tape around the threads
4. Refit the gland in the leaking radiator valve
5. Refill the system
6. Check for leaks

A thermostatic radiator valve leaking water from the pin has to be replaced, but if you want a temporary fix, you could try turning the radiator off when it leaks, as this might help until you replace the radiator valve.

If it’s leaking from a nut on the bottom or side of the TRV, then you should follow the process above for a “leaking radiator valve nut“.

Radiator Drain Valve Leaking

To fix a leaking radiator drain valve, you will need to replace the rubber washer seal inside in most cases.

A radiator drain valve can be part of a radiator valve or on its own on the pipe work.

The rubber washer seal on a radiator drain valve normally gets damaged by over-tightening it when closing. It really doesn’t need to be that tight, as it’s rubber.

They tend to get crushed or pushed into the valve and can be a nightmare trying to remove the old washer.

You might need to replace the head of the valve that the washer sits on which you take from another valve.

How to stop radiator drain valve leaking:

1. Drain the central heating system
2. Remove the head of the radiator drain valve with some water pump pliers
3. Remove the black rubber washer
4. Fit new washer or head
5. Refill the central heating system
6. Check for leaks

You might need to replace the radiator drain valve.

Radiator Valve Tail Leaking

A radiator valve tail leaking is usually caused by one of three reasons:

• Not having enough PTFE tape on the threads that go inside the radiator
• The radiator valve is not screwed into the radiator enough
• From rusting old radiators

The radiator valve tail leaking is the worst leak to get on a radiator.

Here are three ways to fix a leaking radiator valve tail:

• Tighten the leaking radiator valve tail with an adjustable spanner
• Replace the PTFE tape
• Replace the leaking radiator valve tail

Tighten the Tail

You can sometimes fix the radiator valve tail leaking by turning it clockwise with an adjustable spanner.

This is only possible if it’s sticking out enough and you have enough space to get the spanner in to turn it.

Replacing the PTFE Tape

1. Drain the central heating system
2. Remove the radiator valve with an adjustable spanner
3. Remove the radiator valve tail with an adjustable spanner
4. Clean the tail
5. Wrap some new PTFE tape around the threads (at least 15 wraps)
6. Refit the tail and tighten with an adjustable spanner (make sure it’s very tight or it will leak, add more PTFE if it’s not tight enough)
7. Refit the radiator valve
8. Refill the system
9. Check for leaks

Replace the Radiator Valve Tail

Sometimes the tail will need to be replaced. If so you can follow the same steps above for replacing the PTFE tape.

Radiator Bleed Valve Leaking

A radiator bleed valve leaking will usually mean you need to fit a new the bleed valve.

If the bleed screw is sitting in a bigger nut, then you can try tightening the nut with an adjustable spanner.

If that doesn’t work you should add some PTFE tap or jointing compound:

1. Close both radiator valves (or drain the system)
2. Open the bleed screw with a bleed key to release the pressure and catch the water until stops coming out
3. Remove the radiator bleed valve or screw (whichever is leaking)
4. Add some jointing compound or PTFE tape around the threads
5. Refit the radiator bleed valve
6. Refill the radiator or heating system
7. Bleed the radiator
8. Check for leaks

Radiator Valve Leaking When Turned Off

If you have a radiator valve leaking when turned off, then you could try opening the valve slightly to see if it stops.

You should follow the steps above for a leaking lockshield valve if this does not work. You might have to replace the radiator valve.

In my experience, a radiator valve leaking when turned off is usually on ancient radiator valves that are worse for wear and should probably be replaced.

Conclusion

Fixing a leaking radiator valve is easy most of the time with no need to remove the radiator.

Once you have found exactly where the leak is coming from it should be a case of tightening the nut.

Draining the system and adding some jointing compound or PTFE tape is the next level to fix a radiator that is leaking. This is a lot harder but needs to be done.

Failing that, replacing the leaking valve might be the only solution.

Feel free to ask me any questions in the comment section below and I’ll try my best to help.

Please share this post if you found it helpful.

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Leaking Radiator Valve FAQs

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Can a leaking radiator valve be repaired?

Yes, a leaking radiator valve can be repaired. It might have to be replaced, but most of the time a leaking radiator valve can easily be repaired with an adjustable spanner.

Is a leaking radiator valve an emergency?

A leaking radiator valve is not really an emergency. It can cause damage to flooring, electrics, and possibly the rooms below the leak, but I have not seen an emergency situation come from a leaking radiator valve in over ten years of plumbing.

You should definitely get a leaking radiator valve fixed as soon as possible, as water damage can really mess things up if left for any length of time.

Can a leaking radiator valve cause boiler pressure to drop?

Yes, a leaking radiator valve can definitely cause boiler pressure to drop.

A leaking radiator is the most likely cause of a boiler pressure dropping, so if your boiler keeps losing pressure after repressurising, you should look for a leak on your radiator valves and boiler.