air vent on old hydronic radiators

digger

why are some manual vents near the top of the radiator while others are located about a third of the way down the side?

Long Beach Ed

Hot water vs. Steam

Radiators used for hot water are tapped for the vent at the top where an air bubble would collect.

Radiators used with steam are tapped at the side, about a third off the bottom as the air is pushed from the top and bottom nipples to the center of the last section.

Radiators are traded from one system to another and people with drills make mistakes.

Long Beach Ed

digger

thanks for simple explaination.
I have a drill. Would it be a mistake to place the air vents at the tops of these radiators? I have already moved one as an experiment, and it worked.

Steamhead (in transit)

Is this

a steam or hot-water system?

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