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How To Bleed a Radiator: A Simple 8-Step Process To Try

How To Bleed a Radiator: A Simple 8-Step Process To Try

A hot water radiator is one of the oldest but most effective ways to heat a home. With that being said, these units don’t come without some issues on occasion. Have you noticed that only the bottom of your radiator is hot while the top remains cold to the touch?

If you’re experiencing this problem, an accumulation of air is likely to blame. To an inexperienced homeowner, this may sound like a complicated issue that a plumber needs to address.

Before you get a plumbing company on the phone, hear us out. You can perform a technique called “bleeding” on your radiator to address this problem yourself. It’s quite simple and shouldn’t take too much time out of your day.

Below, we will cover how to bleed a radiator on your own. Plus, we’ll explore the benefits of performing this task and what causes the need for it.

What Are the Benefits of Bleeding a Radiator?

After bleeding your radiator, you will first notice your unit begin to function properly. It will be warm no matter where you touch it and perform its job optimally. However, completing this task won’t only result in a warmer, cozier environment.

This simple technique is a great way to cut your energy bills down and increase the efficiency of your home’s heating processes.

Why Has Air Built Up in My Radiator?

A radiator that’s cold to the touch likely has air built up in it. This accumulation of air may have been caused by any one of these factors:

  • The pump was initially installed above the supply tank
  • Leaks in your unit
  • Rust in your piping
  • Excessive sludge in your piping

Signs You Need to Bleed Your Radiator

If you notice any of the following signs, you may need to bleed your radiator:

  • Your radiator is cold on the top but warm on the bottom
  • Your entire radiator is cold
  • You notice mold growth or dampness around your home
  • Your radiator is rattling, gurgling, gulping, or making other weird noises because of the trapped air

Brown Heater On A Wooden Floor

Step 1: Turn on the Central Heating

Start by switching on the central heating in your home. Switch your radiator on too and turn it up fully. If you aren’t sure how to do this, review your particular user manual.

If your home has several radiators, turn these on and fully up as well.

Wait until all of the units in your home have fully heated up until you move on to the next stop. This will typically take a few minutes, but the time will vary depending on your units’ efficiency. We advise you to wait around thirty minutes for the best results.

Step 2: Feel the Unit for Cold Spots

Once your radiator has heated up, touch it all over to find out if there are cold spots present.

If your home has more than one radiator, check all of the units around the same time. Some may be working perfectly while others may need to be bled.

To be safe, we highly recommend that you wear gloves during this step. Hot water radiators are no joke. The Old House Journal Magazine reports that radiators can get up to 180°F or hotter. If you’re not careful, you can acquire third-degree burns from touching a hot unit.

If you notice that your units take a long time to heat up, are cold in some spots, or are making gurgling noises, you will need to bleed them.

Step 3: Turn Your Central Heating Off

Once you determine which units you need to bleed, you should turn your central heating off. You may keep the radiator intake valves open.

Never attempt to bleed your radiators with the central heating on. If you do not turn off your central heating, the water pumps will suck more air into your heating system when you open up the bleed valves. This will be counterproductive to the bleeding process.

Step 4: Wait for Your Radiators to Cool Down

Once you switch off your central heating, you need to wait for your radiators to completely cool down. Touch them all over with gloves on to determine when they are cool. Do not try to bleed a radiator even if it’s slightly warm.

If you attempt to bleed a warm radiator, you may:

  • Experience boiling water spurting out of the bleed valve
  • Ruin the effectiveness of the bleeding process, as your unit’s contents won’t be settled completely

While you wait, you should do two things:

Assemble Your Supplies

To complete the bleeding process, you will need the following supplies:

  • A radiator key: A radiator key will help you open and close the bleed valve. Some modern radiators have valves that you can loosen and tighten with an ordinary flathead screwdriver. However, you should try to find the original key that came with your radiator. This device will give you more control over how you close and open the valve.
  • A cloth: You will hold this cloth as you turn the radiator key. It will help you get a good grip and prevent your hand from slipping.
  • A container: You will use this container to catch any water that leaks from an old radiator.
  • Several old towels: You will place these towels on the floor around your unit to protect your carpet from water leaks as you work.

Plan Your Route

It’s common practice to bleed the radiators on the ground floor first. Start with the ones that are furthest away from your home’s boiler. Then, you can proceed to the ones on your home’s second and third floors.

Step 5: Locate & Loosen the Bleed Valve

Once your radiator has completely cooled down, locate the bleed valve. On most units, this valve should be on top (either the left or right side). It looks like a round hole with a small square inside of it.

This valve is where you will be releasing all of the air and excess water. To keep the mess to a minimum, lay your old towels on your floor and set up your container.

At this point, you will loosen the bleed screw. Place the radiator key into the square portion of the bleed valve. If you are using a screwdriver, position the blade into the groove.

Grip your key or screwdriver with your cloth and turn the bleed screw counterclockwise. Only perform half of a turn to let the air escape. You will hear a hissing sound as air makes its way out.

Do not complete a full turn, as this will cause water to violently pour out once all the air has escaped.

Step 6: Wait for the Hissing to Stop

Once all the air escapes, the hissing sound will stop. Water will begin to come out of the valve in a dribble or small jet.

At first, you may notice a sputtering mix of water and air. Wait until the valve produces a steady stream of water. At this point, all of the air will be gone.

You may have to wait anywhere between 30 seconds to a couple of minutes to fully bleed a radiator.

Step 7: Re-tighten the Bleed Valve

Position your key or screwdriver properly and turn it clockwise to re-tighten the bleed screw. Don’t turn the screw too tightly, as this may damage the valve. Wipe down excess water to prevent rusting in the future.

Repeat these steps for every radiator in your home.

Step 8: Turn Your Central Heating On Once Again

Once you bleed all of the radiators that need it, you may turn on your central heating again. Give your radiators time to heat up and ensure that they all feel warm all over. Ensure the bleed valves are not leaking.

Also check to make sure your boiler is showing an optimal heating pressure level. Industry experts recommend that a boiler’s heating pressure be around 12 to 15 psi. Bleeding a radiator may cause the pressure of your heating system to drop. If your boiler’s pressure is too low, heat won’t be able to reach some of your home’s radiators.


Bleeding a radiator is a simple DIY solution you can perform at home. As long as you follow the instructions in this guide and use caution, you should not need to call a professional. This fix is a quick one, so your unit should start working properly immediately.

If you don’t feel comfortable completing this task yourself, be sure to contact the experts at All Dry USA! Our team is fully trained to ensure your radiator is in top condition.

Our experts are also available to address more serious problems with your home’s radiators caused by water, fire, or smoke damage. Get in touch with today to take back control of your home!


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