How to bleed a radiator: a step-by-step guide

Why do I need to bleed a radiator?

When the temperature is single digits outside, the last thing you want is an underperforming radiator!

Over time, air can become trapped in your radiators which can affect how hot it gets.

Removing this excess air by ‘bleeding’ your radiators means your home will get warmer faster, making it a more comfortable space and saving you some cash on your heating bills. It’s a no-brainer!

When should I bleed my radiators?

The main way of knowing when it’s time to bleed your radiators is when they’re not performing properly. If you’ve got your heating turned up but aren’t feeling the benefit from your radiators, there’s an easy way to check if they need bleeding.

With the heating on, carefully place your hand on the radiator. It should feel nice and hot all over. If your radiator is hot at the bottom but gradually gets colder as you move your hand up, that’s because trapped air is stopping the hot water from heating your radiator fully.

Your radiators may also make a gurgling or whistling sound, which can often be caused by trapped air.

You may need to bleed your radiators once every year or 2, but once you know how easy it is, this won’t be a problem!

Tools for the job

Bleeding a radiator doesn’t require loads of fancy equipment or a degree in plumbing. Here’s what you need:

• Radiator key or flathead screwdriver, depending on the valve
• A small bowl or container
• Cloths or towels
• Gloves

Before you begin

It’s vital that you turn off your heating and let the radiators cool completely before you start bleeding them. You don’t want to risk splashing yourself with hot water!

How to bleed a radiator

In what order should I bleed my radiators?

Yes, it matters which order you bleed your radiators! Bleed the downstairs radiators first (if your home has 2 floors or more) and start with the radiator that’s furthest from the boiler. Then head upstairs and bleed those, again beginning with the radiator furthest from the boiler.

Step 1: Locate the release valve

Check the top edge of your radiator to find the release valve. On most radiators, it’s a small, square pin, but some have a slot in the middle which you can open with a flathead screwdriver.

Step 2: prep the area

Lay some towels or cloths on the floor underneath the release valve to mop up any drips or spills from the radiator. Have a bowl handy to catch any water that may come out of the release valve.

Step 3: Open the valve

Using your radiator key or flathead screwdriver, gently turn the valve anticlockwise until you start hearing a hissing sound. Use a towel to help you grip the key if the valve is a little stuck.

There may be some dripping water at this point, so keep your towels handy!

Step 4: Close the valve

Keep the valve open until the hissing sound stops and water starts coming out of the valve, then turn your radiator key clockwise to close it.

Mop up any excess water, and you’re done. Onto the next one!

Step 5: Check your boiler pressure

Your boiler pressure will probably drop once you’ve bled your radiators, so top up the pressure if necessary to the recommended bar.

Depending on the model of your boiler, there’s normally 2 valves on the pipes leading to your boiler which you can turn to top up the pressure, but always read the manual first and consult a pro if you’re unsure.

Step 6: test your heating

Now that everything is good to go, turn your heating on and test each individual radiator for cold spots. Repeat the process on any radiators which still have air in them. Also check to make sure that your valves are fully closed.