Radiator Bleed Key UK: Which Key, and How to Bleed a Radiator

Flat illustration of a white radiator with a brass bleed key in the valve, a drip cup catching water and a long radiator brush

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Nartel radiator bleed keys are in the Amazon UK DIY and Tools top 30 this morning, at #23. With the heating back on, are your radiators cold at the top? That usually means trapped air, and a bleed key is the fix.

The short answer: most UK radiators take a standard square bleed key, and a solid brass two pack costs very little, so keep one in a kitchen drawer. A bleed key with a drip catcher saves a towel, and a long radiator brush clears the dust that collects between the fins.

Last updated: 29 October 2026

On the Amazon UK DIY and Tools chart today: Nartel radiator bleed keys, pack of 2, at #23. This is a practical UK shopping shortlist on amazon.co.uk. It does not invent prices, ratings or claims beyond what the listings state.

Standard radiator bleed keys

Bleed key with a drip catcher

Radiator brushes for the dust between the fins

Open the live listing on the day you buy, as pack sizes change.

How do you bleed a radiator?

  1. Turn the heating off and let the radiators cool
  2. Find the bleed valve, a small square inside a round fitting at one top corner
  3. Hold a cloth under the valve, fit the key and turn it anticlockwise a quarter turn
  4. Air will hiss out; close the valve as soon as water appears
  5. Do the downstairs radiators first, then upstairs
  6. Check the boiler pressure gauge afterwards and top it up if it has dropped, following your boiler manual

Which key do I need?

  • Most modern UK radiators use a 5 mm square key, which is what the standard brass keys above are
  • Some radiators have a slotted valve that a flat screwdriver turns instead
  • If the valve looks different or is seized, check with a heating engineer rather than forcing it

Still losing heat? See our draught excluder strips guide and thermal curtains guide.

Use the Amazon product and search links above to compare options on amazon.co.uk. This is a UK shopping shortlist for radiator bleed keys, not plumbing or gas safety advice.

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