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

If your radiator feels cool at the top, but the bottom is still warm, it likely means you’ve got air trapped inside and it has risen to the top. Letting this air out, known as bleeding the radiator, will fix the problem and allow your radiators to work properly. Not only will this keep your home nice and warm, you’ll also save money due to increased efficiency. Read on to find out how to bleed your radiators.

Step 1: Turn the heating on

Before you get started, you’ll want to turn your heating on. Ensure that each radiator is turned up fully and give them time to heat up fully (radiators further away from your boiler will take longer to warm up). Once they’ve had time to warm up, check each one for cold spots.

Step 2: Feel each radiator

To find out which radiators are causing you problems, you need to feel each one to identify cold spots. Make sure that you use gloves so you don’t burn yourself. You’ll be able to tell which radiators need bleeding as they will that takes a longer time to heat up or have a cold top section.

Make sure you check all radiators in your home at the same time, as you may find you need to bleed more than one. Always start by bleeding the radiator on the lowest floor and furthest from the boiler first, before moving through each one in sequence.

Step 3: Allow the radiator to cool

Before bleeding your radiators, turn off your heating and allow the hot water in the system to cool. If your radiators are still warm, don’t attempt to bleed them, as hot water will spurt out when you open the valve. This will also give the radiator a chance to settle, making the bleed more effective.

Step 4: Gather your tools

To bleed your radiators, you will need:

  • Radiator key
  • Cloth
  • Old towels
  • Container to catch any drips

Radiator keys can be easily obtained fairly cheaply from a local DIY shop. Some newer radiators have a valve that can be turned with a flathead screwdriver, so check this first. A standard radiator key will also work, too, and is typically preferable as it gives you more control over the valve.

Step 5: Locate the bleed valve

The location of the bleed valve varies from model to model, but will typically be found at the top of the radiator on one of its ends. You can find it fairly easily: it looks like a round hole but with a small square inside. This is where you will use your radiator key to release air and water, so set up your towels on the ground nearby.

Step 6: Turn the bleed valve

Use the radiator key to loosen the valve by turning it anti-clockwise. A small turn will usually do it, no more than a half turn. This will allow the air to escape without allowing the water to pour out. You should begin to hear a hissing noise as the air escapes, and you may get small droplets of water, too.

Step 7: Wait for water

When the air has been removed, water will start to trickle out of the valve. This will initially be a spluttering mix of air and water, but once the stream of water becomes steady, the radiator has been bled. It should usually take around 30 seconds, but can take longer with larger radiators.

Step 8: Close the valve

You can now retighten the bleed valve using your radiator key or screwdriver. It’s important that you don’t tighten it too much as this can damage the valve. Use your cloth to wipe up any remaining water that may have spilled.

Step 9: Rinse and repeat

You can now repeat steps 5–8 for any other radiators that need bleeding. Keep going until all the required radiators have been done. Remember, start on the ground floor with the radiator that’s furthest away from the boiler before moving on to the upper floors of your home.

Step 10: Check your work

Once you’re done, you can turn the heating back on and check your work. Check all radiator panels and ensure there are no leaks and drips. It’s possible that some of your radiators may need to be bled again. You also need to check the boiler pressure and, if necessary, top up the pressure using the filling loop on your boiler.

What to do if your radiator is not getting hot after bleeding

Nine times out of ten, bleeding your radiators will fix the issue of your radiators not getting hot. Unfortunately, this is not always the case, and there are some other potential issues that could be causing this problem.

If a pin is stuck down on your radiator’s thermostat valve (the put that allows you to control the temperature), then it may not be heating as it should be. If you remove the cap, you will notice the valve pin, which can sometimes get stuck in the off position, preventing water from flowing into your radiator. Use a set of grips to grab the pin movie it up to allow the water to flow again.

If this doesn’t work, the problem could be more serious and may need a power flush to remove sludge from your system, so we recommend contacting a Gas Safe registered engineer to look at the problem for you.

Bleeding your radiators doesn’t have to be a pain. Follow this simple step-by-step guide and your heating system will be operating at 100% in no time.

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