Bleed a Hot Water Radiator
Cold spots at the top of a radiator mean air trapped inside, blocking hot water from circulating. 2-minute fix; do it at the start of every heating season.
Tools
- ✓~$5 at any hardware store; some radiators take a flathead screwdriver instead
- ✓For catching water
Materials
- No materials needed.
Steps
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1
Turn the heating system on
Run the boiler for 15 minutes so radiators warm up — this pressurizes the system and pushes air to the top of each radiator. Feel each radiator: cool top + hot bottom = needs bleeding.
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2
Find the bleed valve
Small square or hex valve at the top of one end of the radiator. Hold a rag or cup under it.
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3
Turn off the heat
Shut the system off before opening valves — bleeding a pressurized hot system can spray scalding water.
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4
Open the valve slowly
Turn the key counterclockwise 1/4 to 1/2 turn. You'll hear a hiss as air escapes.
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5
Close when water flows
When water (not air) starts dribbling out, the radiator is bled. Close the valve.
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6
Repeat for each radiator
Work from the lowest floor to the highest. After all radiators are bled, check your boiler's pressure gauge — top up if it dropped below the green zone (usually 12–15 psi).