Perhaps a stupid question...
The ON / OFF valve on one of my 1900s radiators does not turn. Pictures below. The radiator is in a permanent "hot" state.
Is the "valve" (handle and "small nut") indicated below a replaceable part? Or must I replace the entire pipe elbow + valve to replace the valve?
The small nut turns easily with a pipe wrench. I have not tried unscrewing it fully so as to not create a (possible?) geyser...
The boiler/radiators are off. If the valve is replaceable, will I be able to simply unscrew it and replace it (without all the water spraying out, without draining, etc.)? If not, can this individual radiator be drained sufficiently by itself? Or must the entire building's radiator system be drained?
I will explore finding a way to turn the handle, and re-use this valve. But assuming that's not possible, what are my options?
All images: http://imgur.com/a/Ar8iU