No Water In Radiator? Here’s Why

This is gonna be a short one, for one reason. If you have no water in your radiator, there’s really only one likely cause. If the fix we provide doesn’t solve the issue, it’s likely that you’ll need to call a professional for help. We could go with you through every possible bit of your central heating system that’s not working, but a plumber will do it better. I know that’s not what a lot of people want to hear, but it’s the truth!

The most likely cause for no water in a radiator is an airlock in the system.

Let’s just dive right in, because this is a relatively easy fix that should hopefully solve your issue, once and for all.

Fixing an Air Lock in Central Heating

Okay, so first things first – what is an airlock? Well, it’s exactly what it sounds like! Air has locked your central heating system from providing water where it needs to go. This is equally common in radiators and taps, really anywhere you have running water in the home. Don’t worry too much, because this is a normal problem that won’t cause other larger issues if addressed.

In short, air gets trapped in your water pipes because, well, it’s air. It goes pretty much wherever it wants, including into your plumbing. It’ll usually form bubbles that will go with the water, but sometimes that doesn’t happen. They can get caught in a bend in the plumbing, collecting and forming one master bubble. Okay, that’s not what it’s actually called, but I thought it sounded cool, so we’re going with it.

Because air rises, the most common place to find air bubbles is in the highest section of your plumbing. So if you have an upstairs tap or radiator that’s not working, this is likely the cause. They’re also especially common in hot water lines, as they have lower pressure than cold water lines. That makes them an incredibly common affliction with radiators.

Okay, but how do you fix it?

The Solution

Okay, here’s everything you’ll need to do to remove an airlock:

  1. Turn off your central heating and the radiator in question at the lock-shield and TRV end.
  2. Latch open any motorised valves.
  3. Bleed your radiator.
  4. Remove the entire radiator bleed point.
  5. Attach a hose (you may need an adaptor) to where the air bleed was.
    1. If needed, most plumbers will help you out with finding the right adaptor if you ask nicely.
  6. Run the hose outside (or to a bath/shower if that’s not possible)
  7. Open your TRV and flush the water out. You’ll hear air coming out – that’s what we want. Wait 10-15 seconds and close the TRV. (It takes very little time to remove air pockets.)
  8. Repeat the process on your lock-shield end.
  9. Close both valves and remove the hose.
  10. Reinstall your bleed point and remove the hose.
  11. Ensure your motorised valves are closed again
  12. Top up and repressurise your system.
  13. Turn on the heating and test. Allow your radiator ~an hour to refill.

In case you’re unsure how to repressurise and top up your central heating system, do the following:

Top Up and Repressurise

To repressurise:

  1. While your heating is off, remove the traya on the bottom of your boiler. (Either plastic or metal.)
  2. Remove the filling key from the tray.
  3. Place it in the key manifold, usually directly next to the manifold (square) nut.
  4. Turn it to the unlocked position (there’s usually a padlock open/closed symbol).
  5. Turn the manifold nut counterclockwise with a wrench.
  6. Watch your pressure gauge and turn the nut back when it reaches 1.5 bar.
    1. If it goes too far, turn the release knob on your nearest radiator – it will release hot pressurised air, so be careful.
  7. Turn the key back into the locked position.
  8. Replace the key and tray.

To top up:

Simply add water to your feed water valve until it’s at the proper level.

Note, also do this while the boiler is off. You can and will burn yourself if you don’t.

Final Thoughts

This hopefully should have resolved your problem. If you still have no water in your radiator, it’s likely time to call a professional for help. The only thing you can easily do from home is to clear an airlock and top up/repressurise your boiler. Anything else should be left to the professionals. This is because it is entirely possible that there’s something you can’t see happening behind the scenes.

So if you’ve tried everything above to no avail, sit back, make a drink, and call the professionals. You’ll get to watch as they do what they do best, and you won’t have to lift a finger. It’s entirely possible that they’ll find a blockage or something else along the line that is causing the issue, and have it back up and running in no time.

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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.