How to bleed a radiator without a radiator key, according to heating experts

You don’t need a radiator key, but you should exercise caution

A dining table and chair with a vase of flowers and a window
(Image credit: Future PLC/James Merrell)

A radiator key is specifically designed to bleed radiators, but if you’ve lost or broken yours, you’ll probably want to know how to bleed a radiator without a radiator key. And that’s exactly why we’ve asked the experts for their top tips on what you can use instead… and how

Knowing how to bleed a radiator is something every homeowner needs to have in their wheelhouse. Ideally, you should bleed radiators every single year as part of regular central heating maintenance or when you notice that your radiators are cold at the top but hot at the bottom. But you don’t technically need to have a radiator key to complete this task. 

There are alternative tools you can use to bleed a radiator, and we’ve consulted with the experts to provide a step-by-step guide on how to bleed a radiator without a radiator key while also bringing the potential risks to light.

How to bleed a radiator without a radiator key 

‘Bleeding a radiator is an essential task for maintaining an efficient central heating system and ensuring your radiators heat up properly. If you don’t have a radiator key, you can still perform this task with some alternative tools and methods,’ explains Stephen Day, Operations Director at iHeat. Below, you’ll find everything you need to know about how to bleed a radiator without a radiator key.

What you’ll need

  • Flat-head screwdriver or Allen key
  • Old towels
  • Bucket 


1. Find an alternative tool

Unfortunately, radiator bleed valves can’t be turned by hand, which means that you’re always going to have to find an alternative tool to help you out. But if you have a flat-head screwdriver in your toolbox or stashed away in your junk drawer, you’re in luck.

Nicholas Auckland, heating expert at Trade Radiators, explains, ‘The flat head screwdriver is the most popular alternative to a radiator key. Most modern radiators made in the last 5-10 years have a small dent where the flat head screwdriver can be inserted into the bleed plug,’ 

picture of nicholas aukland
Nicholas Auckland

Nicholas Auckland is a heating and energy expert with over 10 years of experience in the industry, as well as the Managing Director of Trade Radiators. Nicholas is dedicated to finding the best heating solutions for every need, as well as optimising energy usage, reducing costs and helping others live with lower costing energy bills. Nicholas has become a trusted leader in the industry, frequently collaborating with the media and other partners to assist with cost of living issues and other home-related problems.

2. Identify the type of radiator you have

While a flat-head screwdriver should help you bleed a radiator when you don’t have a radiator key, it’s important to understand that this is not a one-size-fits-all solution. This is especially true if you have older radiators.

‘Some panel radiators, like the older ones, probably don't have the option to use a flathead screwdriver. Bleeding the radiator in this situation is more challenging but not impossible. You should attempt using alternative tools like an Allen key, a small spanner, or a pair of pliers,’ says Nicholas. 

A houseplant display with a radiator

(Image credit: Future PLC)

3. Prepare the area and turn the heating off

Bleeding a radiator can be a messy business. So, prepare the area by placing some towels underneath and around the bleed valve to protect your floor from any potential drips. 

If you’re really concerned about making a mess, you could also consider placing a bucket underneath the bleed valve to catch any stray water. 

Of course, you should never bleed a radiator while the heating is on, as the hot water and steam could result in serious burns. So always ensure you turn off your heating and allow your radiators to cool before moving on to the next step.  

4. Open and then close the valve

Next, you need to open the bleed valve, which would normally be done using a radiator key. But if you’re using an alternative tool, use that instead. 

Stephen suggests, ‘Carefully insert your tool into the valve and slowly turn it anti-clockwise. A quarter to a half turn is usually enough. You should hear a hissing sound as the air escapes.’

‘Once all the air has escaped, water will start to leak out. This is your cue to close the valve. Turn it clockwise to tighten it, but be careful not to overtighten as this can damage the valve.’

A dining table and chair with a vase of flowers and a window

(Image credit: Future PLC)

5. Check the pressure

Although the process of bleeding your radiators can make them more energy efficient, this process can also cause the pressure in your boiler to drop. So, before you pack up your tools and turn the heating back on, you should always check the pressure gauge on your boiler. 

Stephen says, ‘If it’s too low, you may need to repressurise your heating system.’ This task will be different for every boiler, so it’s best to consult your manual for the exact instructions on how to do that. 

6. Test your heating

When you think you’ve successfully bled your radiators and your boiler is at the correct pressure, you can then check your handiwork by testing the heating. If you have been successful, all of your radiators should warm up quickly and evenly. 

If they don’t, you may have to repeat the process, or it may be that you need to look into how to flush a radiator or how to balance a radiator

White painted room with windowsill nook, shelves, and radiator

(Image credit: Future PLC/Katie Lee)

Risks to consider when bleeding a radiator without a radiator key

While it’s certainly possible to bleed a radiator without a radiator key, you should always exercise caution when using something that wasn’t designed for that specific task. In fact, doing so could spell disaster for yourself and your heating system if you’re not careful. 

Nicholas explains, ‘These alternative tools can potentially damage the bleed plug permanently due to the fact that they're not specifically designed for this purpose. Even if you successfully open the bleed valve and release the air, you may encounter difficulties when attempting to close it again, which could result in too much water loss and even burns.’

‘If you don't have a radiator bleed key and your radiator can't be fixed with a flathead screwdriver, first think about whether you can wait until you can get a bleed key or call in a professional who will have all the correct tools.’

‘Although it's frustrating if the issue can't be solved immediately, using a bleed key is the only truly appropriate tool for this task. It'll help you clear the issue without damaging your radiator, so it's always better to wait a little longer for a proper solution rather than choosing a temporary and forceful fix that could cause damage.’

Of course, if you’re not confident in how to bleed a radiator without a radiator key, we’d always suggest consulting a professional before trying any DIY plumbing. Although the parts and labour will cost you, seeking professional help could ultimately save you a lot of money in the long run if you were to do something wrong. 

Dining room with gallery wall and wall and pendant lights with blue and green glass shades

(Image credit: Future PLC/Anna Stathaki)


What if I don't have a radiator bleed key?

If you don’t have a radiator bleed key, you can use an alternative tool. A flat-head screwdriver will always be your best bet, but if you find that this doesn’t work you could also use an Allen key or a pair of pliers to turn the bleed valve instead. 

How do you bleed a radiator when the key won't turn?

If a radiator key doesn’t turn, it may signify a problem with the valve itself. Nicholas says, ‘99% of radiator keys are universal, and so should fit your radiator if it was installed in the last 35 years or so. Check to see if either the key or the valve is misshapen, then call in an expert who'll be able to sort out your problem. You will potentially need that specific part of your radiator replaced.’

Can I use a screwdriver to bleed a radiator?

Yes, you can! Just make sure that you use a flat-head screwdriver, as this will be the best fit for your bleed valve. 

It’s also important to note that while screwdrivers can be used to bleed most radiators, that doesn’t mean that they will bleed all radiators. 

If you have older radiators, you may need to use an Allen key or a pair of pliers. Be careful when doing so, though, as these tools are not specifically designed for this task and could do more harm than good.

Now you know how to bleed a radiator without a radiator key, it’s time to get started! 

Lauren Bradbury

Lauren Bradbury is a freelance writer and major homes enthusiast. She graduated with a Bachelor’s degree in English and Creative Writing from the University of Chichester in 2016, before dipping her toe into the world of content writing. After years of agency work, writing everything from real-life stories to holiday round-ups, she decided to take the plunge and become a full-time freelancer in the online magazine world. Since then, she has become a regular contributor for Real Homes and Ideal Home, and become even more obsessed with everything interior and garden related. As a result, she’s in the process of transforming her old Victorian terraced house into an eclectic and modern home that hits visitors with personality as soon as they walk through the door.