How to Bleed Air From Radiators Without a Radiator Key
Whilst bleeding the air from a radiator is normally an easy DIY task, like most jobs without the right tools it can become a real chore.
If you have problems with your radiators when your central heating system is turned on, then the first thing to check is if there is any air trapped in the system.
Trapped air will make a radiator feel cold at the top or will prevent the radiator from heating up at all, and the way to solve this is by bleeding the air from the radiator.
Bleeding the air from a radiator with a rad key is simple, but what if you do not have a rad key? Can you still bleed the air out and fix your heating problems?
In this article, we show you how to solve this problem and get your heating to work properly in no time at all.
Tools Required
- Flat Head Screw Driver
- Small adjustable Wrench
- Old Rag
- Small Container
Alternative Ways to Bleed a Radiator
If you have lost or do not have a radiator key, you can still bleed the air from your radiators using other tools you may have in the house or your toolbox.
The first alternative to using a radiator key is to use a flat head screwdriver. Most, if not all radiators manufactured over the last 10-15 years are fitted with bleed valves that include a slot that allows for a flat head screwdriver to be used to turn the bleed plug.
Always use an old cloth or small cup to prevent drips or leaks and hold this under the bleed valve whilst you slot the screwdriver into the bleed pug and open the valve by turning it anti-clockwise.
Any trapped air in the radiator will escape as the valve opens and there will be a hissing sound as it moves past the plug.
All the air is gone when only water passes the valve and the hissing noise stops. Quickly close the valve with your screwdriver by turning it in the opposite clockwise direction.
Another alternative if your radiators are not fitted with a slot for using a flathead screwdriver is to use a small socket that will fit over the bleed plug.
This type of bleed plug is more common in older radiators over 15 years, and this type of radiator is more difficult to bleed without using a radiator key but the task is not impossible.
Other tools such as an Allen key may fit the bleed plug or a small adjustable spanner can often be used to grip the square flats on the bleed plug.
I do not recommend using pliers as they tend to slip and will damage the bleed plug making it very difficult to remove, and if you succeed you may not be able to close the valve again.
Take care when using any alternative methods as you may cause damage to the bleed plug, and if you manage to open the bleed valve and allow the air to escape, you may struggle to close it again.
It may be a better option to wait until you can find or buy the right radiator key for your system. Using the wrong tools may end up in replacing the radiator and costing you both more time and money.
Read our associated article on how to properly bleed air from your central heating for more great plumbing tips
Are Radiator Bleed Keys the Same?
The difference between radiator key sizes is usually to do with the age of the radiator. Modern radiators, which have been installed in the last 25 years are typically a standard metric size. Older Radiators may use imperial sizes.
A 5mm square radiator key, which you can buy online or in hardware stores should fit modern radiators in most new homes. Older radiators can be bled by using imperial sizes keys, typically a size 12 key (4.8mm) will fit older radiators.
These keys are often also the same size as keys used for winding up clocks, which were often found in many homes before digital clocks were invented and widely used. If you live in an older house, with older cast-iron radiators it may be worthwhile investing in a set of clock keys ranging from size 8 to size 12 which are available online.
The most common style of radiator key is designed to be held between your thumb and forefinger with either a wide, flat area or pins that form a ‘T’ shape, but you can buy keys that fit multiple screwed fittings like control panel locks, gas meter boxes.
The other end of the radiator key is a small cylinder with a square slot that will fit over the radiator bleed plug or valve.
Whatever style or type of radiator you have in your home, I recommend having at least a couple of radiator keys, which are kept safe in different places, so that you always have one available should you need to bleed the air from your central heating system.
Find out more about central heating and plumbing in our other great Plumbing articles
This article was written by: Richard Quinton – The DIY Help Desk Owner, Engineer & technical specialist.
Richard is one of the key partners in The DIY Help Desk team. He is a qualified Engineer, writer, and publisher, educated to Master’s level. He is a keen advocate of DIY and home improvements.
Richard enjoys helping others to learn new skills and reach their goals and believes that passing his knowledge and experience on through his writing is an effective way to positively impact the lifestyles and well-being of others on a larger scale.
