How to Bleed a Radiator? A Step-by-Step Guide

Bleeding a radiator and deciding on when to do this are essential for efficiently heating your home. It can help save you money on your energy bills, whilst also helping you do your bit for the environment by using them only when needed. Your radiators are just as important as your boiler, so if you have an inefficient heating system, you may not get your money’s worth during the colder days and months.

Understanding how to bleed a radiator is key to ensuring its health and longevity too, but do you know where to start and how to do this correctly? In this step-by-step guide, you’ll find out how to bleed your radiator, why doing so is important, when to do this, and what you’ll need before starting. As the UK’s leading supplier of radiators, at Stelrad we know that regular maintenance of your radiators is important to get the most out of them and ensure efficient use, so use our guide to understand more about this simple, yet important, task.

What Does Bleeding Radiators Mean for Homeowners?

Bleeding radiators is the act of removing unwanted air from the heating system that builds up over time. So, how does air get into your radiators? Unwanted air is a side effect of the heating and cooling of water within your heating system. Air bubbles are created during normal use, so over time this air will congregate within the system as it has nowhere to escape to – this is where bleeding the radiators comes in.

A heating system will have a mix of chemicals to ensure that the inside of the system doesn’t rust. However, the build-up of air can be an additional factor in whether your heating system will stay rust-free. A black magnetite sludge may appear in your heating system that can settle at the bottom of your radiators and impede water circulation around the system. With air naturally created with use, this can also contribute to poor circulation, meaning noticeably colder radiators when turned on. The combination of air, water and metal is a recipe for rusting, so bleeding the radiators not only ensures better heating efficiency, but also prevents adding to potential rust build-up and anything worse such as leaks or burst pipes.

As a homeowner, you’ll want to ensure you are bleeding your radiators properly and regularly to avoid this happening. The last thing you want is to invest in designer radiators that do not last due to poor maintenance, so doing your bit with this quick task every now and again can ensure better care.

When & How to Bleed a Radiator

Bleeding your radiators doesn’t need to be a laborious task and is not something you will need to do every day or week. Even if you have old radiators that have seen plenty of use over the years, as long as you’re regularly maintaining them, bleeding them doesn’t have to be done constantly – although you may want to consider upgrading to modern energy-efficient radiators if you’re looking to change. Here are some common questions to ask yourself before deciding to bleed a radiator when your heating system is turned on:

  • Is the radiator turned on? Check the valve to ensure it is
  • Is the top section of the radiator cool to the touch, while the bottom of it is warm?
  • Does the entire radiator feel cold?
  • Do you hear gurgling noises as your heating system is running?

If you notice cold spots in your radiator, it often indicates that air is trapped inside which has risen to the top. Therefore, you need to release (or bleed) the air trapped in your radiator. This allows the radiators to heat effectively when in use again. If the entire radiator feels cold, it could indicate a bigger issue, but you should always check the radiator valve is on and allow time to heat up. Any radiator noises such as gurgling or popping sounds you can hear when it’s turned on and warming up may indicate air in the system too.

The good news is many of the above symptoms can be quickly resolved by bleeding your radiators. As it is a natural occurrence within the heating and cooling of water, it is a very common problem experienced by all radiator owners at some point. You can easily fix this with a few simple tips, but how often should you be checking your radiators and then bleeding them?

You should consider bleeding radiators in your home at least once a year – each one in your property. You may be surprised how much air you can get out of radiators that seem to be working normally too, so addressing the issue before it gets worse is ideal. As you may have a few months of the year, such as during the summer, where you do not use your radiators much, if at all, you may want to bleed them when you start using them again.

We recommend doing so during the colder months as this will make it much easier to diagnose any potential issues as you will be using your radiators regularly. Of course, you can choose to bleed your radiators at any time of year and as often as you like, but at least once a year should be sufficient.

Bleeding a Radiator – Should I Call a Professional

You may notice numerous cold or lukewarm radiators in your home. If your radiators are not getting hot, then unfortunately it could mean there’s a larger issue with your home heating system even if you have bled your radiators. We have a friendly team here at Stelrad to help should you need further advice on your radiators, but you should contact a local plumber to see if your boiler is the issue or to see if you need to flush your heating system completely.

Another sign of an inefficient home heating system is when the radiators on the ground floor are hot, but the ones in the upstairs rooms are not. This can suggest water circulation issues in your home heating system, where the pump may be struggling to move hot water through the system. If you notice this while bleeding your radiators, we recommend calling a professional to check your full system. It’s better to have peace of mind with your radiators and boiler if you sense a bigger issue.


After diagnosing the issue, you will need to release the bleed valve on your radiators to bleed them. You may want to ensure you have your radiator keys/a flathead screwdriver and cloths or towels to hand before you start and follow these steps to avoid any mishaps:

Step 1 – Turn Off Your Heating System

turn off your heating system













  • Ensure your heating system is turned off so that the pump is not running.


Step 2 – Wait for The Radiators To Cool Down

  • Once identifying which radiators are affected, wait for the radiators to cool down.
  • This is to ensure any hot water doesn’t harm you whilst bleeding the radiator.

Time for radiator to cool down














Step 3 – Have Your Radiator Keys and Cloths/Towels Ready