How to Bleed Radiators without a Key

Close-up of Radiator Bleeding Key

No matter how new or high quality your radiators, it’s essential that you take the time to ‘bleed’ them each year before the cold weather season when they’re likely to be used; as part of their routine maintenance.

Radiators need bleeding regularly to maintain the air pressure within them and avoid pockets of air from grouping. However, if a radiator feels cold even when the heating is on (and it’s turned on), or has noticeably cold patches, it needs bleeding outside of routine maintenance in order to re-balance and re-start its optimum performance.

The best time to bleed radiators even before cold patches or underperformance is noticed is in the summer, before colder weather settles in and the radiators need to be turned on to heat the home.

The term ‘bleeding’ in this sense simply means to release air. Bleeding a radiator is usually done with a radiator bleed key, which slots into the ‘bleed screw’ of the appliance and is supplied upon purchase. Exactly how to bleed a radiator is universal between models, although you’ll find lots of information on how to use a radiator bleed key and how to do the process online.

Are Radiator Bleed Keys Universal?

If you don’t have one, or can’t find one, you may be considering where to buy a key to bleed a radiator. These can be purchased from most hardware stores for a nominal fee (usually between about 50p and £3), but you will need to know which radiator bleed key you need – radiator bleed key sizes and shapes vary. There are over 10 types of key, so it’s not uncommon for homeowners to buy one, but get home and find their newly purchased radiator bleed key doesn’t fit the bleed screw. If you're unsure of how to bleed a radiator or find the key tough to move, seek the advice and guidance of a heating professional.

Older radiators tend to use bleed keys that fit old, imperial measurements, so if your radiator is of a well-known brand name and fairly dated, it may fit a standardised set of keys. Ask a professional or heating expert for more info.

Radiator bleed keys are not to be confused with radiator joining keys, which are used to join the columns of radiators that are larger than standard sizes. These are more expensive accessories and don’t have any impact on radiator bleeding, nor will they fit a radiator’s bleed screw.

If you have a very old radiator, it may have a bleed valve rather than a bleed screw. In this case, look at the top of the radiator on the left or right size for a hole with a raised square shape in the middle. The valves should be able to be opened with your hand, but wrap a cloth around your hand to avoid mess and to protect your skin in case it’s stubborn to budge. In most cases, a radiator this old will need replacement rather than just a bleed to restore full performance.

Where to Buy a Key to Bleed a Radiator?

If you don’t have a correctly fitting key, then read on – we know how to bleed radiators without a key, and there are several ways to easily (and safely) do so!

Exactly what to use in place of a bleed key if you don’t have one depends on the shape of your radiator’s bleed screw. If your radiator bleed screw is shaped like a square nut, a regular socket may fit over the nut. Spanners can also work and many people just use pliers, but be careful: this can easily scratch, chip or even dent and damage the screw itself, and any damage to it will inhibit its future use.

Bleed screws shaped like security screw heads may be opened by needle nose pliers slotted into the shape within, and those with hexagonal sockets may be opened with the relevant sized Allen key or flat-headed screwdriver.

Many new models of radiator have bleed screws designed with a small flat line orifice to allow for an easy screwdriver turn.

Most of these substitute items for radiator bleed keys, as well as the keys themselves, are available in hardware stores or the home aisle of a supermarket, but should you require a specific radiator key type, get in touch with the manufacturer or retailer.

Unfortunately, radiator bleed keys aren’t universal; but there are lots of alternatives that can be used to open your bleed screw and release the trapped air within. Don’t hold off on bleeding your radiators until you can find the key if there’s a reasonable easy alternative.

If you bought your radiator from Great Rads, contact us to discuss what you’re after and we’ll strive to help where we can – and if we have one spare, we’ll pop it in the post to you!


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