How to Bleed a Radiator Without a Key
Your home’s radiators, as well as its wider central heating system, are probably one of the most important parts of your home.
This is particularly true during the colder, winter months when the temperature plummets and you need to stay comfortable and warm in your property. If your radiators are not working correctly, it can have a detrimental effect on your home. In addition to feeling unpleasant, a freezing cold house can have a wider impact on people’s health as well as potentially damaging a property’s interior.
One of the best ways to ensure your radiators continue to perform at an optimum level is to bleed them. This process ensures air consistently moves throughout the system while also reducing pressure on the overall system.
Bleeding radiators is a fairly straightforward household task, and normally involves using your radiators’ bleeding key. But what if the key has become lost or misplaced?
Even if your key is missing, it is still essential that radiators are properly bled, and in this article, we’ll answer the question ‘how to bleed a radiator without a key’. – Read on to find out more.

What happens if you don’t bleed a radiator?
Before we take a look at the various ways you can bleed a radiator without a key, let’s take a closer look at the problems that can arise if you neglect to do so.
Not bleeding your radiators can create a wide range of problems including the following:
A less efficient heating system
Over time, it’s normal for your radiators to suffer from some wear and tear, and performance can drop as a result. One of the most common problems that can occur is for air to become trapped within sections of a radiator. When the air becomes trapped, hot water is unable to properly circulate. This reduces the efficiency of the radiators and the entire central heating system. This means your home will not become as warm as you’d like. Furthermore, when air becomes trapped it can create air pockets. These air pockets can cause cold spots within the radiator, resulting in uneven heating, including certain rooms being colder than others. Again, this will contribute to a less efficient heating system.
Increased wear and tear
When air becomes trapped in the system, it can cause your boiler and central heating system to work even harder as it attempts to circulate hot water. This puts increased strain on the system and often leads to higher energy consumption and premature wear and tear. This increased level of wear and tear can then lead on to needing costly repairs or even system replacements.
Higher bills
Bleeding radiators help to make your radiators and central heating system more efficient. Not only can a less efficient system contribute to a colder home and uneven heating, but it can also impact your pocket, too. This is because you’ll likely need to consume more energy to get your property to a comfortable temperature. The more energy you use, the higher your utility bills will be, so it’s clear to see the financial benefit of ensuring the system is as efficient as possible. As well as this, intense pressure on your system could require it to need repairs or be replaced which can be extremely expensive.
Noisy radiators
When air becomes trapped in a system, it can cause the radiator to become extremely loud and noisy. You may experience gurgling or strange banging noises as the water tries its best to pass through. This can be a very disruptive experience, especially as you’re trying to relax in your home. If you hear these noises in your radiators, it could indicate that there is a problem that needs to be addressed.
Corrosion
If air is left trapped in the system for an extended period, it can lead to damaging corrosion of the radiator and its various components. This can cause radiator leaks, further reduce the radiator’s efficiency and lower the lifespan of the system.
How to bleed a radiator without a key
So, you know you need to bleed your radiator but can’t find your key. Sounds like a disaster, right? Well, while it’s certainly not ideal, it isn’t the end of the world.
There are ways you can bleed a radiator even without the key, but you will need to assess what kind of fitting or plug your radiator has. This will determine the appropriate method you will need to use to bleed the radiator.
Different radiators will have different valves, and the alternative to the bleed key will depend on which type you have in place.
Slotted bleed screw: A slotted bleed screw valve looks like a big nut with a screw at its centre. If your radiator has this kind of valve, you can use a standard flathead screwdriver as an alternative.
Square nut: If you have a square nut in place, you could use a spanner or pair of pliers to open the valve. However, a suitable socket from a socket set is the best option.
Hexagonal nut: Some bleed nuts have hexagonal sockets. In these instances, your best bet is the use of pliers.
Hexagonal sockets: Similarly to hexagonal nuts, hexagonal sockets are also commonplace on radiators. If this is the case for you, you can use an Allen key or flathead screwdriver.
Once you’ve selected the most appropriate tool for your radiator, you can begin the bleeding process.
Insert your chosen tool into the bleed slot and turn it counterclockwise to bleed the air out of the radiator. Be sure to keep an eye on the valve until the bleeding has been completed. This is because some water will start coming out of the valve, and you’ll need to close it to prevent water from going all over your floor.
It’s also wise to check your boiler pressure after the radiator has been bled. Boiler pressure tends to drop after bleeding, so check the pressure remains within the recommended level of between one to two bars. If it has dropped below one, follow your boiler’s instructions to increase the pressure to a suitable level.