Bleeding Your Radiators: When and How To Safely Bleed Your Radiators

Sometimes it isn’t the boiler itself that causes issues with your heating; it can also be other components malfunctioning. There are certain times when you may need to bleed your radiators, such as when cold spots appear at the top of the radiator. Bleeding your radiator allows hot water to flow through your heating system. In this blog, we will explore when you should bleed your radiators, and how to safely do it.

When to bleed your radiators

There are a variety of reasons why you may need to bleed your radiators, including:
-Cold spots at the top of the radiator: This is the most common reason why a radiator needs bleeding. This occurs when the air becomes trapped in the radiator and is unable to escape, meaning the hot water cannot circulate through the radiator like it normally would.
-Damp or mould: If you start seeing mould or a room is damp after little usage, then this might be caused by your radiator. Mould is caused by bad circulation and humidity, so it is important to bleed your radiator if you start to notice that the room is damp or has mould.
-Rattling radiators: Noisy radiators, whether it be a rattling or gurgling sound, should be bled and checked for issues by a heating specialist. As there are a variety of reasons why a radiator might be making unusual sounds, it is best to also get it checked out in case there are any risks or if the radiator is close to breaking completely.

What tools do I need to bleed my radiators?

There are only two tools that you will need to successfully bleed your radiators: a radiator bleed key and anything that can catch water (such as a jug or a cloth). Radiator bleed keys can typically be found in hardware shops, but if not, a flat-headed screwdriver may also work.

How do I bleed my radiators?

Before starting to bleed your radiators, you must first identify which radiators need bleeding, as not all of your radiators may need it. You should start with the radiators closest to the boiler on the ground floor. From there, you should work your way backwards, away from the boiler. You should work your way from storey to storey.

Step 1: Make sure your heating is turned off and all of the radiators are cold.
Step 2: Place your jug or cloth under the bleed valve and insert the bleed key.
Step 3: Turn the bleed key anti-clockwise to loosen the valve; this will allow the trapped air to escape.
Step 4: Once the water starts to escape, turn the key clockwise to tighten the valve. When water starts to escape, this means that all of the trapped air has been released.
Step 5: Repeat on all radiators.
Step 6: Once all required radiators have bled, you should check the pressure to ensure it has not dropped.
Step 7: Turn on the heating to check if the radiators are working.

Additional Information

Can the heating be on while bleeding your radiators?
The heating MUST NOT be on while bleeding radiators due to how hot the water is. As some water may escape when bleeding the radiators, it could cause a burn if it comes into contact with your skin. In addition to this, more air may get into the radiator while the valve is loose if you have your heating on.

How can I tell if bleeding my radiators worked?
Once all radiators have bled, the heating should be turned back on to test the radiators. You should look for how long the radiators take to heat up, and if there are any cold spots on the radiator. If there are still issues after bleeding your radiators, you should contact a boiler specialist for further guidance.

How often should I bleed my radiators?
Though not essential, it is recommended to bleed your radiators once every 6 months to ensure that there are no build-ups of sludge or trapped air.

What are the advantages of bleeding my radiators?
There are a variety of benefits to bleeding your radiators such as:
-Efficiency: Your boiler and central heating system will be more effective at heating a room faster if the trapped air is removed regularly.
-Energy-efficient: As the radiators will not lose heat to the trapped air, less energy will be required to heat the room. This results in fewer fuels being burned and therefore is more environmentally friendly.
-Identify issues: If the radiators are already having issues, bleeding them will determine whether the trapped air was causing the problems or not. If bleeding your radiators doesn’t help, you should contact a heating specialist for further assistance.

If you would like a new boiler installed, or need any boiler assistance, please do not hesitate to contact us at or 01274 317169.

Boiler Pressure: A Guide To High Boiler Pressure and Low Boiler Pressure

Boiler breakdowns are never ideal, especially during the winter. One of the most common reasons for a boiler breakdown is the boiler’s pressure being either too high or too low. Boiler pressure isn’t always a big issue, as it can be adjusted without the need of a boiler specialist.

How to check the boiler pressure

As boiler pressure is the most common reason for a boiler breakdown, it is essential to check your boiler pressure. On most modern combi boilers, the pressure gauge can be found either on the front of the boiler or under the control panel. If your boiler is older, the pressure gauge might be located near the pipework. You can use your instruction manual if you are unsure where your pressure gauge is located.

It is useful to do a monthly check of your boiler to identify any obvious issues and to check that your boiler’s pressure is perfect. Boiler pressure may also be brought up during an annual service, so the specialist may fix it on your behalf and identify the cause of the issue. To find out the importance of annually servicing your boiler, please click here.

Standard boiler pressure

Standard boiler pressure is between 1 to 2 bars. Fortunately, most pressure gauges can show you if the pressure is perfect by using red and green sections. The green section means the boiler pressure is fine and doesn’t need changing. If it is in either of the red sections, it means the pressure is either too high or too low. Please be aware that your boiler may still continue to work, even if the pressure is too high or low, so it is important to check and adjust the pressure when necessary.

High boiler pressure

High boiler pressure is not always a serious issue; most boilers have mechanisms to counteract high pressure. Many boilers will shut down if the pressure is too high, or the valve may release some water into a small pipe away from the boiler to resolve the issue.

Signs of high boiler pressure

Unlike low boiler pressure, there are only two simple signs to look out for. If the system has shut down, or the gauge is in the red section, then the boiler pressure is high.

Causes of high boiler pressure

High boiler pressure is usually accidentally caused when adjusting boiler pressure. Sometimes, when fixing low boiler pressure, it might be adjusted too much and cause higher pressure than intended. In addition to this, if a valve is not tightened enough, this can cause too much water to flow, which can impact the pressure. If this is the case, you will need to tighten all valves to stop the overflowing of water.

If your boiler has high pressure and it was not caused by adjusting pressure or by having loose valves, then it is likely that your boiler is faulty, and may need checking for issues.

How to reduce high boiler pressure

In most cases, it is possible to reduce high boiler pressure without needing to contact a boiler specialist. If you follow these steps, but it continues to increase, then you should contact us for further guidance as it could be caused by a faulty boiler.

Step 1: Turn off your boiler
Step 2: Make sure all valves are tightened
Step 3: Once the system has cooled down, bleed your radiators. If you have any issues with bleeding your radiators, contact a professional immediately – it is very easy to bleed a radiator incorrectly!
Step 4: Check the pressure gauge. If the pressure is still high, bleed your radiators again

Low boiler pressure

Low boiler pressure is usually more noticeable than high boiler pressure due to the effects low boiler pressure has on heating the building. On Average, a boiler will need the pressure increasing between every 6 months to 12 months due to the heating system naturally heating and cooling water.

Signs of low boiler pressure

Low boiler pressure can cause no heating or hot water to go around the system due to there not being enough pressure in the system. If you notice these issues, you should check the gauge on your boiler (usually located on the front, on the front panel, or on the pipeline).

Another sign of low boiler pressure is the gauge showing the pressure in the red section. If it is only slightly low, you may not lose hot water or heating to a noticeable degree, so it is useful to check your boiler pressure from time to time to make sure it is not too high or low.

Causes of low boiler pressure

There are three main causes of low boiler pressure:
Water heating and cooling: Naturally, boilers will lose pressure over time due to water heating and cooling within the system. As a result of this, you may need to repressurise your heating system every 6 months – 12 months. If this is the case, this does not mean that your boiler is broken or there are any issues within the heating system, so there is no need to panic.
Small leaks: Sometimes, a leak may occur in the pipelines. These leaks can be so small that you may not notice any water escaping, but over time, the water escaping will build up and cause the pressure to decrease.
Bleeding your radiators: As water can escape when bleeding your radiators, it can slightly decrease the pressure

If you have high boiler pressure and reduce the pressure, you can also cause the boiler pressure to be too low. This is not a common cause of low boiler pressure but can be easily fixed.

How to increase low boiler pressure

Increasing your boiler’s pressure is a simple task and can be done without the help of a professional. By following these steps, you can repressurise your heating system:

Step 1: Turn off your boiler
Step 2: Locate either the filling loop or the keyed filling loop, depending on the type of boiler. The filling loop is a hose that connects to two water pipes, with two levers to control the valves. If you cannot find your filling loop, you should refer to the boiler manual.
Step 3: Turn both levers so they are aligned with the direction of the hose. If this is done correctly, you should hear water starting to run.
Step 4: Keep an eye on the gauge and stop the valves once the gauge hits roughly 1.2 bar. Make sure that both valves are closed to avoid high boiler pressure.

Top tip: Do not turn on your boiler straight away, you should wait before using it to check if the pressure is still decreasing. If the pressure continues to decrease, you should look for leaks. You should contact a boiler specialist if you suspect a leak, in order to amend it and receive the most appropriate recommendations for your specific heating system.

If you would like to learn more details about low boiler pressure, read our guide to low boiler pressure here.

In conclusion, usually boiler pressure being too high or too low is not a big problem. As you can adjust your boiler’s pressure, you can fix most pressure issues without the worry of having to call a boiler specialist. However, you should contact a boiler specialist if you have any concerns with adjusting your boiler pressure or you are still having issues after adjusting the pressure.

If you have any boiler concerns or would like a boiler installed, please do not hesitate to contact us at or 1274 317169.