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If you simply want a way to turn a 1-pipe Radiator on and off, ......
The only way to shut off a one pipe steam radiator is to plug the vent .
The above comment by @Big Ed_4
, in @ConservationCrowley
's discussion, Radiator Supply Valve - Why do we need 'em?
, reminded me of something that I've been pondering for a while now:
If you simply want a way to turn a 1-pipe Radiator on and off, why not just insert a valve, such as this, ....
.... between the Radiator and the Air Vent, like this?
The thing that most appeals to me about this approach, is that the "operator" (which means "tenant" in the worst case) can't cause water hammer by opening the valve part-way.