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Bleeding Radiators Order


After discovering that your radiators haven’t been heating up lately or some have developed cold spots, you did some research and found that they need bleeding. But the question is, in which order do you bleed the radiators?

What does bleeding a radiator mean, and is it important?

Bleeding radiators is the act of removing unwanted air from the heating system.  You wouldn’t want trapped air in your heating system is as it will lower your boiler’s efficiency. For instance, it can impede hot water circulation around the system that causes cold spots or even contribute to rust settling in awkward places in the radiators.

Bleeding your radiators at least once a year may seem inconsequential, but it adds up in terms of serving your radiators for efficiency and durability. Free-flowing hot water around the systems means less energy consumption by the central heating that keeps your bills low in turn.

If you find yourself paying massive energy bills and not getting sufficient heating, your heating system may have some air trapped in it.  Luckily, resolving this problem is quite simple since you just have to bleed your radiators.

When should you bleed your radiators?

Bleeding your radiators is recommended at least once a year to keep your boiler at optimal functioning. If you also had your heating system drained recently to replace broken radiators or install a new boiler, you should bleed the radiators before using the system again.

However, as you wait to perform the annual bleeding of your radiators, here are some tell-tale signs that you may need to fast-track the process and do it immediately.

Radiators cold at the top but hot at the bottom

Patchy warm radiators are the most common sign that your radiators need immediate bleeding. Cold spots to the top of your radiators essentially imply that air bubbles have collected in the radiators, which impedes hot water from freely and effortlessly circulating and heating the radiators.

Releasing the trapped air solves the problem of patchy warmth in the radiators hence heating your home effectively. It will also prevent your radiators from failing, and this will save you several hundreds of pounds in replacement costs.

The entire radiator is cold

The purpose of the radiator is to warm your room. So finding it cold even when the central heating is on indicates that it needs immediate attention. A cold radiator implies that air is not necessarily trapped in the radiators but further along in the pipework, therefore restricting hot water meant to flow into the radiators. While bleeding can sort the problem out, it is advisable to get a professional heating engineer to prevent complications in the future.

Mould and dampness

Mould grows and strives in cold and damp places. Therefore, if your notice mould and mildew around your house, it essentially signifies that the radiators are not heating up effectively or not working altogether. From this, you can deduce that air is trapped in the radiators and is preventing the free flow of hot water. Bleeding your radiators will get your radiators functioning again.

Rattling radiators

An efficient radiator works in silence, so if your radiators make funny noises, like gulping, gurgling, and rattling, it needs attention to ensure that the problem does not run deep. This problem may be due to various reasons, and bleeding your radiators may help.

Where does the air in the system come from?

Trapped air in the radiators necessitates bleeding. But given that the central heating system is airtight, you are probably wondering how the air got into the system.

Well, the air usually enters the system when new water enters the system from an expansion tank or when routine maintenance is being done.  The pump can also introduce air into the system as it turns.

Where to start when bleeding a radiator

Depending on the number of floors in your home, you should begin by bleeding the downstairs radiators first and work your way up. The best practice is to start with the radiator furthest from the boiler that cools fast after turning the central heating off. It is essential to turn off the central heating before opening the bleeding valve because some water pumps will suck in air into the radiators, a problem you wanted to alienate in the first place.

What you will need to bleed your radiators

Here are a few items you will need to bleed your radiators, most of which are readily available in your home:

  • Radiator vent keys. They are available in almost all hardware. You can also acquire one online. Brass radiator vent keys are a good choice as they tend to be tough
  • You will need a rag to soak up any excess water
  • Glasses and a pair of gloves. Water coming out of the system while bleeding is dirty water and potentially contaminated with chemicals.
  • A bucket

Safety while bleeding

There is the risk of injuries while bleeding the radiators, for instance, burns and scalding. There are steps to be taken to keep these risks at a minimum. It is imperative to turn off your central heating before venting your radiators. With the central heating system off, if any problems arise, you are dealing with a flow of cold water than a potential flow of hot water.

Guide how to bleed a radiator

Follow the simple steps below to bleed your radiators and become a true DIYer!

  • Turn your heating on. Turn your heating to maximum heating and wait for all your radiators to heat up. The time it takes to heat the radiators will depend on the number of radiators in your home. Therefore, be sure to give yourself plenty of time.
  • Check each radiator for cold spots. After all the radiators heat up, you should embark on searching and deducing which radiators need bleeding. Radiators with patchy warmth or gurgling sounds are a perfect place to start. While looking for cold spots, wear a thin pair of gloves as the radiators can be scorching.
  • Turn the heating off and allow it to cool. It is essential to turn off the heating and give enough time for the water in the system to cool down. When you start bleeding your radiators, there is minimal risk of burns.
  • Find the first radiator to bleed. If you need to bleed more than one radiator, always start with the one on the ground floor furthest from the boiler. Continue in that manner and work upwards.
  • Locate the radiator bleed valve. You will usually find the bleed valve at the top and side of your radiator. The bleed valve is the small metal square or screw that is inside the surrounding nut.
  • Place a cloth below the radiator bleed valve. Put your rag on the floor beneath the bleeding valve to protects your floor from discoloured water drips.
  • Insert the radiator bleed key and open the bleed valve. Using your bleed key, turn this square vent anti-clockwise until you hear the hiss of air as water forces it out. Be careful not to turn the vent too far and always leave some of the threads holding the vent in to prevent you from losing the vent plug and causing an accident. It is better to vent the radiator slowly.
  • Close the bleed valve. Once the hissing sounds stops and water starts to leak out, it means the trapped air has escaped. Turn the bleed key clockwise to close the valve.
  • Bleed your other radiators. Repeat the above processes for any other radiators in your home that need bleeding.
  • Check your boiler’s pressure. If the boiler pressure is too low (below 1 bar), you will need to repressurise the system. If the pressure is normal (between 1 and 2 bars), it is okay to switch your heating on and check that your radiators are operating as they should.

If the radiators are still cold after bleeding, it implicates build-up of sediments inside the appliance, and you may need to flush your system.

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