How to Bleed a Radiator in 8 Quick Steps

Don’t worry—it’s not as painful or difficult as it sounds

Photo: d3sign / Moment / Getty Images
Photo: d3sign / Moment / Getty Images
Paige Bennett
Written by Paige Bennett
Contributing Writer
Updated Aug 22, 2024
SKILL LEVEL
Easy
COMPLETION TIME
25 minutes
COST
$0
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What you'll need:
TOOLS
  • Radiator bleed key
  • Flat-head screwdriver
  • Needle-nose pliers
  • Towel
  • Work gloves

You’ve settled into the couch after a long day at work, and you’re looking forward to catching up on your TV shows. But the room feels chilly, and you notice the radiator is making some distracting banging sounds. Rather than shiver and try to ignore the noise, you can spend less than the time it takes to watch one episode of a show and bleed the radiators to fix the problem. Learn how to bleed a radiator, which gets rid of air pockets that prevent hot water from circulating through your heating system, to get things working properly (and quietly) again.

How to Bleed a Radiator

Learning how to bleed a radiator system is easy with our eight straightforward steps and tips.

Read more

  1. Locate the Radiator, Heat Switch, and Bleed Valve

    Before you start bleeding the radiator, there are a few things you’ll want to locate. Start by identifying the radiator on the first floor that is farthest from the boiler—even if you have one noisy or cold radiator, it’s best to bleed them all at the same time, and you’ll start with the one farthest away from the boiler. Then, locate the heat switch, as you’ll need to turn off your central heating, and locate the radiator bleed valve. This valve is usually at the top of the radiator on one of the sides.

  2. Turn Off the Heat

    A man turning the heat off
    Photo: zoranm / E+ / Getty Images

    Radiators can get pretty hot, and you don’t want to be touching hot metal while you’re trying to work. Not only that, but bleeding a radiator while the heat is still on could cause it to take in more air, and you’ll need to bleed the radiator again. Turn off the central heating, then wait about 15 to 20 minutes for the radiators to cool down. Note that you don’t need to know how to turn off a radiator for this step; shutting off the central heat will do.

  3. Lay Down a Towel

    While you don’t want to let out a lot of water, you can expect a little bit to dribble out of the bleed valve once it is open. To avoid an extra mess to clean up, simply lay a towel down around the floor beneath the bleed valve. You could also set up a small bucket here to catch any drippings.

  4. Open the Valve

    Use the radiator bleed key to open the bleed valve. If you don’t already have a radiator bleed key, you can pick one up at your local home improvement store or order one online for about $5. Otherwise, you can use a flat-head screwdriver or needle-nose pliers to open the valve, turning counterclockwise just slightly, about half of a turn.

  5. Let the Excess Air Escape

    Now that the valve is open, you’ll start to hear a hissing sound as the trapped air escapes. At this point, a few drops of water may also leak out. This will take less than 20 to 30 seconds. You’ll know the bleed is complete when a stream of water starts to leak out.

  6. Gently Close the Valve

    A woman fixing and bleeding air from central heating
    Photo: m-gucci / iStock / Getty Images Plus / Getty Images

    When closing the valve, you want to work carefully. Tightening it too much could cause the valve to break off, particularly on older radiators. Use the radiator bleed key, or whichever tool you used to open the valve, and turn it clockwise for about half of a turn. This will tighten and close the valve.

  7. Repeat With Other Radiators

    It’s best to bleed all of the radiators at once, so after finishing up with the first one, move to the next radiator. You’ll want to work from the radiator farthest from the boiler, then move from radiator to radiator, getting closer to the boiler. If you live in a multistory home, start on the first floor following this pattern, then repeat the pattern on the next floor.

  8. Turn on the Heat

    Once you’ve bled all of your radiators, turn the central heat back on. Now, your home should feel warm and cozy all throughout the rooms.

DIY vs. Hiring a Pro

Radiator repairs cost about $100 to $500, and having a pro bleed the radiator costs about $100 to $200. If you opt to DIY, you may spend a few bucks to buy a radiator bleed key if you don’t already have in your toolbox. Otherwise, this project costs nothing in supplies. Bleeding a radiator is an easy task for most homeowners, even if you’re a beginner. 

However, if you turn the central heating back on after bleeding and notice the radiators are still not heating up properly or are making weird noises, it’s time to hire a local boiler repair person. The problem might not be your radiators at all. It could be a problem with the boiler, which is a complex heating system and difficult to service without proper training. Or you may need to budget for the cost to replace a radiator, which is another challenging job best left to the pros.

Frequently Asked Questions

When it comes to bleeding a radiator, the goal is to let out trapped air rather than letting out the water. Naturally, some water will dribble out when you open the valve to let out the air. But you don’t want a lot of water to leak out. Just leave the valve open long enough that the hissing noise stops, meaning the air has escaped, and just a dribble of water comes out of the radiator.

There are a couple of signs that will tell you it’s time to bleed the radiator. If the radiator is making noises, it’s typically because of trapped air, which you can release by bleeding the radiator. You can also test the radiator by turning on your heat and then placing your hand near the top and bottom of the radiator. If you feel cold spots, particularly at the top of the radiator, it’s time to bleed it.

You’ll want to bleed your radiators at least once per year, typically in the fall before you plan to turn on the heat. Bleeding a radiator is a regular part of your heating system maintenance, and you’ll need to do this regularly to keep these units running efficiently. You should also bleed radiators any time they start making noise, like gurgling, hissing, or banging.

If you have multiple radiators, start by bleeding a first-floor radiator that is farthest from the boiler. Work your way toward the boiler on the first floor before moving to the next floor, where you’ll again start by bleeding the radiator farthest from the boiler. Continue this pattern for radiators on each floor until they’ve all been bled.

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Learn more about our contributor
Paige Bennett
Written by Paige Bennett
Contributing Writer
Paige Bennett is a professional editor and writer with experience covering design, DIY projects, food, health, and travel, and holds a bachelor's degree in journalism from Ohio University.

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