Bleeding your radiators is a simple and essential maintenance task that can significantly improve the efficiency of your central heating system.
Over time, air can get trapped in your radiators, causing them to heat unevenly and reducing the overall performance of your heating system.
This guide will walk you through the step-by-step process of how to bleed a radiator, offer some top tips, and how to identify when you might need help from a heating and gas engineer.
Why do you need to bleed your radiators?
Air pockets trapped in radiators can lead to several issues, such as cold spots, gurgling noises, and reduced heating efficiency. And if that's not enough to put you off, you’ll also be sitting in a chilly house.
When air enters the system, it prevents hot water from circulating properly, leading to uneven heating. Bleeding your radiators allows the trapped air to escape, ensuring that your radiators heat up fully and your heating system operates efficiently.
Regular radiator bleeding can help maintain a comfortable temperature in your home and potentially reduce your heating bills by increasing the efficiency of your central heating system. Winner!
Essential tools and materials
Before you begin the process of bleeding your radiators, gather the following tools and materials:
- Radiator bleed key (or a flathead screwdriver for modern radiators)
- An old towel or cloth to catch any excess water
- A small container or jug to collect escaping water
- Protective gloves (optional)
Step-by-step guide to bleeding a radiator
1. Turn off your central heating system
Before you start bleeding your radiators, make sure your central heating system is turned off. This is crucial for safety reasons and to prevent more air from entering the system while you're working.
Allow the radiators to cool down completely before you begin the bleeding process.
2. Locate the radiator bleed valve
The bleed valve is usually located at the top of one side of the radiator. It may have a small metal square (the bleed screw) that fits the radiator bleed key. In modern radiators, you might be able to use a flathead screwdriver to turn the valve.
Familiarise yourself with the location of the bleed valve on each radiator you plan to bleed.
3. Prepare for bleeding
Place an old towel or cloth beneath the bleed valve to catch any drips or excess water. Have your small container or jug ready to collect any escaping water. This preparation will help you avoid any mess during the process.
4. Insert the radiator bleed key
Insert the radiator bleed key into the bleed valve. If you're using a flathead screwdriver, fit it into the slot of the bleed screw. Ensure you have a firm grip and are ready to turn the screwdriver or radiator key anti-clockwise.
5. Open the bleed valve
Turn the radiator bleed key anti-clockwise about a quarter turn. You should start to hear a hissing noise, which is the sound of the trapped air escaping. Be cautious and only open the valve slightly. If water begins to escape immediately, close the valve slightly until only air is coming out.
6. Wait for the air to escape
Allow the air to escape until you see a steady stream of water flowing from the bleed valve. This indicates that all the trapped air has been released. The hissing noise will stop once the air is fully out.
This process may take a few seconds to a couple of minutes, depending on how much air is trapped in the radiator.
7. Close the bleed valve
Once a steady stream of water comes out, close the bleed valve by turning the radiator bleed key clockwise until it is securely tightened. Ensure that the valve is fully closed to prevent any leaks.
8. Check the boiler pressure
After bleeding all the radiators, it's important to check the boiler pressure. Bleeding radiators can sometimes cause a drop in pressure within the central heating system.
Check the pressure gauge on your boiler and ensure it is within the recommended range (usually between 1 and 1.5 bar for most systems).
If the pressure is too low, you may need to top up the water in the system according to your boiler’s instructions.
Read our full guide on increasing your boiler pressure for more information.
9. Turn on your central heating system
Turn your central heating system back on and check that all radiators are heating up evenly. Walk around your home and feel each radiator to ensure there are no cold spots and that the entire radiator is getting warm.
Top tips for bleeding radiators
So, now that you’ve read our step-by-step guide on radiator bleeding, it is important to digest all our top tips before getting started.
- Bleed your radiators regularly: It’s good practice to bleed them at least once a year, preferably before the heating season begins.
- Start with the downstairs radiators: If you have a multi-story home, start bleeding the radiators on the ground floor and work your way up. This helps ensure all the air is pushed out effectively.
- Use the right tools: For modern radiators, always use a proper radiator bleed key or a flathead screwdriver. Using the wrong tool can damage the bleed valve.
- Listen for gurgling noises: If you hear gurgling noises or notice cold spots on your radiators, it’s a sign that they need bleeding.
- Check for leaks: After bleeding, check around the bleed valve for any signs of leaks. Tighten the valve if necessary to prevent water from escaping.
When to call in a JustFix professional
While bleeding radiators is a simple task that most homeowners can handle, sometimes it’s best to call a professional.
Get in touch with a qualified heating and gas engineer at JustFix, the home of high-quality service at affordable prices.
If you notice persistent heating problems, such as radiators that remain cold after bleeding or significant drops in boiler pressure, it could indicate a more serious issue within your heating system.
Our teams of Fixers work nationwide to provide you with professionals for fair, fixed prices. When you book online with us, we'll match you with a qualified local heating and gas engineer who can check your central heating system at a time that suits you.
FAQs about bleeding radiators
Do you bleed the radiator when heating on or off?
You should always bleed a radiator when the heating system is turned off. Bleeding a radiator while the heating is on can cause hot water to spray out and potentially burn you. Additionally, it ensures that the pressure in the system is stable and prevents air from being drawn into the system during the bleeding process.
What happens if you let too much water out of a radiator?
If you let too much water out of a radiator, the overall pressure in your central heating system can drop. This may result in the boiler shutting down or the heating system malfunctioning. If this happens, you’ll need to repressurise the system by adding water through the boiler's filling loop until the pressure gauge indicates a normal level.
How to bleed a radiator if the valve is worn?
If the bleed valve on your radiator is worn or damaged, you may need to use a flat-head screwdriver instead of a radiator key. Carefully turn the valve counterclockwise to release the trapped air. If the valve is too damaged to operate, it might be necessary to replace it or call a professional to avoid causing further damage to the radiator.
How much water should come out when bleeding your radiator?
When bleeding a radiator, only a small amount of water should come out once all the trapped air has been released. Typically, you hear a hissing noise as the air escapes, followed by a steady stream of water. Close the valve promptly to prevent excessive water loss, which could lead to a drop in system pressure.
What are the signs your radiator needs bleeding?
Signs that your radiator needs bleeding include cold spots, particularly at the top, while the bottom is warm, gurgling or hissing noises coming from the radiator, and an overall reduction in heating efficiency.
Additionally, if your radiators are taking longer to heat up or the heating system is not warming your home evenly, these could indicate trapped air that needs to be released by bleeding the radiator. Another sign is if the radiator remains cold when the heating is on, especially the upstairs radiators, suggesting air pockets prevent proper water flow.
