How to Bleed Radiators: Step-by-Step Guide for Beginners

Air trapped in radiators makes them heat unevenly, forcing your boiler to work harder. Bleeding radiators (releasing this air) takes 5 minutes per radiator and can lower heating costs by 10-15%. It's a free maintenance task every homeowner can do.

Why Do Radiators Get Air?

• When the heating system is first filled or topped up
• After draining the system for repairs
• Natural gas separation from water over time
• Leaks that let air enter when pressure drops
• Corrosion inside pipes that releases oxygen

What You'll Need

• Radiator bleed key (cost: EUR 2-5) or flat-head screwdriver
• Flat container or cup to catch water
• Old towel or cloth
• Gloves (water may be hot)

5-Step Bleeding Process

1. Turn off the heating system and let radiators cool for 30 minutes.
2. Locate the bleed valve (small brass nipple at the top corner of the radiator—usually one side only).
3. Place the cup under the valve to catch water drips.
4. Turn the bleed key slowly (counter-clockwise) until air hisses out. Once only water comes out, stop.
5. Turn the key back clockwise to close. Wipe any spills immediately.

Check Your Boiler Pressure Afterward

After bleeding multiple radiators, check the pressure gauge on your boiler (usually located at the front). Normal pressure is 1.0-1.5 bar (the green zone). If pressure dropped below 1.0, you may need to top up the system by opening the filling loop valve (check your boiler manual).

When to Call a Professional

• System pressure keeps dropping after refilling
• Radiator has no visible bleed valve (sealed system—needs specialist)
• Boiler is losing pressure rapidly (signs of leak)
• Radiators remain cold at top after bleeding

Bleeding radiators is a simple maintenance task that costs nothing but can noticeably improve your heating comfort. Do it in autumn before the heating season starts, or whenever you notice cold spots at the top of radiators.