How to bleed your radiator

15th June 2022

With over 84% of the United Kingdom using gas heating systems, the likelihood is that at some point, you will have to start bleeding your radiators periodically to ensure efficiency and maximum heating throughout your home. Over time and with continuous use, air bubbles are trapped in radiators, preventing hot water from circulating throughout the house properly. Air in radiators stops them from heating up as quickly as they should, therefore reducing the efficiency of your household heating system and costing you more money as a result. However, bleeding your radiators is a relatively straightforward process, and the best part is you don’t have to be an expert to do it!

Signs Your Radiator May Need Bleeding

Thankfully, there are some very clear indicators as to whether your radiator may need bleeding. The most obvious sign is from your radiator not getting hot when the central heating is active. This can generally be isolated to a couple throughout the house, depending on the age of the heating system, while widespread radiator failure could be an indication of a more serious boiler issue. Other common signs that your radiator needs bleeding include:

The top of the radiator not heating up. While cold spots on radiators are a recognisable sign of air building up, the problem will generally start at the top of the unit. This is due to the air bubbles rising in the central heating and gathering at the top of the unit, causing it to be significantly cooler than the lower half.
Another indication of performance issues is damp patches or condensation build-up around/ above the radiator. While this is less common, it is an indicator that it may not be heating up sufficiently.
Creaking radiators are another sign that the system may need bleeding. This is generally caused by an irregularity in air pressure that causes vibration and the subsequent creaking sounds.

However, before you start bleeding radiators it is important to check for more serious problems. Check that there is no water underneath the radiator or that there is no rust around the system – either of these problems could be an indication of a leak or boiler issue.

15th June 2022

How to Bleed a Radiator

Due to its simplicity, you only need a selection of household items, before starting the bleeding process, such as a dry cloth and a large bowl. The only specialist kit that is required is a radiator key, a small and cheap appliance that is available at most DIY stores. To bleed your radiator correctly, you just need to follow a few simple steps:

Turn off your central heating. Doing this will prevent you from burning yourself and stop the floor from being soaked with excess water.
Find the release value. It’s generally located on the top and on the side of the radiator and is identifiable by the groove that will match that of the radiator key.
Twist the key anti-clockwise, releasing air in the radiator. It is important that you do this with a cloth or bowl ready to catch the dripping water. As the valve is turned, there will be a hissing sound as the pressure is reduced, indicating that the process is working.
Once the hissing stops and water begins to trickle out of the valve, tighten the screw clockwise, making sure not to over-tighten and cause damage.
Wipe any excess moisture off the radiator to avoid rust build-up.

After this, it is prudent to check the pressure gauge on your boiler as the process of bleeding radiators can cause pressure to drop. If this is the case, you can ‘top up’ the pressure via the filling loop located on your boiler. Alternatively, you can use the ‘hot test’ method by simply turning on your central heating and waiting for the radiator to heat up. You can then check for cold spots on the radiator. This process may need to be performed once or twice a year, depending on the age of your system; however, if this is a more regular requirement for your boiler, it could be a symptom of an underlying problem.

Long Term Benefits

Knowing how to bleed a radiator is essential to avoid paying extra for heating bills. By reducing air in radiators, you are ensuring that your heating system remains energy efficient, as well as contributing to the overall health and viability of your boiler.

What if the problem persists?

If your radiators continue to show cold spots after bleeding them, there may be sludge build-up in your heating system that prevents water from circulating properly. However, you won’t necessarily need to replace the radiators. Instead, a powerflush could prove a simple yet quick solution.