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One pipe residential steam system in an old house built 1910.
I have those what look like rusty coils under the floors in the dining room and Living room with air registers on top. They heat ok. I was wondering if I want to replace their old air vents, which one to get. I think the idea was to keep a clean look in those rooms and to avoid radiators. The rest of the house have standard free standing radiators.
They now have the Dole # 4 ( 3/4 in) on three of them and another similar vent on the last one called quick vent #821.