Leaking Radiator Bleed Valve? Here’s Why

Today’s topic is, while frustrating, actually relatively easy to fix (depending on the issue). If you have a leaking radiator bleed valve, you’ll want to keep reading. You likely went to bleed your radiator and noticed something alarming – there’s water leaking out! That can put a damper on your whole day (water puns for the win!) and cause rather serious damage to your home.

Fixing a leaking radiator bleed valve can be done at home without the need for a professional.

Keep reading for a nice little walkthrough on how to replace a bleed valve, fix a leaking valve, and (most importantly) locate the issue.

Why is My Radiator Leaking?

Okay, there’s a lot of ground to cover, so we’re going to hop right into things. Leaks can come from a wide number of places in your radiator, from one of the many valves, to the pipes themselves. While a pipe leak is a major issue that needs a professional’s touch, valves are much easier to repair.

You may end up having to replace the valve in question, but that’s normally not too big of a deal. The first thing you’ll need to do, regardless of where the water is coming from, is to locate the leak. Start by drying off the radiator. Next, I personally recommend taking a bit of toilet tissue and just wiping down the radiator slowly. Be sure to get every inch, and take note of where the paper gets wet. This will help you pinpoint where the leak is coming from, making the next part of the job easier.

Fixing a Leaking Radiator

There are (as I mentioned above) a lot of places you can find a leak. Once you’ve located it, you’ll need to fix or replace the part in question. But how do you do that?

Leaking Radiator Bleed Valve

This is the most common source of a radiator leak. After all, it’s specifically designed to let air (and water) out of the radiator.

Of note is that the bleed valve being in a “mid open” position can cause it to leak. It needs to be either fully open or closed.

The spindle packing in the radiator kit that holds the valve can get damaged or simply worn with age. Regardless of the cause, you’ll need to patch or replace it. I personally recommend that you do both – patch it up, then replace it once you have the time. The next step is really only a temporary solution, anyway.

To patch a leaking radiator bleed valve, do the following:

  1. Turn off your heating and radiator, and allow it to cool.
  2. Drain it of all water that you can through your bleed valve, leaving the valve open. You’ll want a bucket or bowl and towels, as this can be well over 10 litres of water depending on the model.
  3. Shut off the supply valve (the bit that lets water in) and the lockshield valve.
  4. Undo the union nut connecting the feeder pipe and the radiator, dumping all leftover water out – there will likely be at least a little.
  5. Wrap plumber’s tape around the male end of your valve, enough to create a temporary seal.
    1. Again, this won’t permanently solve the issue, but patch it.
  6. Finish by tightening the nut and reopeing all valves you closed. You should be able to switch the radiator on without leaks. Once you do, you can close the bleed valve again.

To Replace a Bleed Valve

Now we get onto the permanent fix – replacing your bleed valve. The above should have given you a moment of moisture-free time, but it won’t last. Now – to replace a bleed valve:

  1. Purchase the proper bleed valve from your radiator’s manufacturer.
  2. Turn off your radiator, draining it of water, just as above.
  3. Unscrew all nuts connecting your feed pipe to the valve, removing the old valve.
  4. Clean the threading of your new valve with a stiff-bristled brush.
  5. Wrap plumber’s tape around the threading of the new valve’s adapter.
  6. Screw the adapter into the radiator by hand, leaving it snug but not too tight.
    1. You should be able to remove it by hand. If you tighten it too far, it can cause damage to the valve or radiator thread – that’s no good.
  7. Replace the bleed valve cap, tightening all nuts you loosened, and place the new valve onto the pipe thread.
  8. Test and enjoy your handiwork!

Other Potential Causes

There are a few other spots that could be the cause of your leak. If you found a leak that’s coming from somewhere other than the bleed valve, these are the most common culprits:

  • Valve spindle – The spindle is the shaft centre to your valve. If you replaced the valve and still found issues, this is likely the cause. You can fix it by doing the following:
    • Undo the gland nut and wind a lot of plumber’s tape over the spindle. You can also cut ~20 cm of tape in a super narrow strip, winding it around the spindle. Carefully push the shaft deeper into the valve, then redo the nut.
  • Corrosion – This is also a common issue. After all, radiators are metal and hold a lot of water. As the parts in your radiator age and wear down, they can spring an interal leak or capture moisture, leading to corrosion. You can temporarily patch it with the plastic resin as a seal, but the only concrete solution is to replace the radiator and add a rust inhibitor to it.
    • A common sign of corrosion is sludge clogging the radiator and pinhole leaks. These are often caused by a buildup of pressure caused directly by the corrosion sludge.

Final Thoughts

If you have a leaking radiator bleed valve, you can both patch and replace it with ease. Before assuming that’s the source of the issue, though, it’s good to properly pinpoint the leak. I find that tissue paper is great at finding moisture, which will help you locate the leak. Once you’ve found the leak, you’ll want to patch your bleed valve as shown above.

After you’ve patched the bleed valve, you have a bit of time to find a replacement. Do not pretend that all is well – it isn’t. You will still need to replace the valve, as the patch is exactly that – a temporary patch job. Replace your valve, and test for corrosion or a faulty spindle. Once that’s all done, you should have a fixed radiator. If not, sit down, make a drink, and call a professional. They’ll get it sorted for you.

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About the Author Harry Thompson

Involved in home renovations throughout his life, Harry is an expert in everything to do with home and garden DIY. In his spare time, he enjoys cooking and tending to his garden.