next week i have to change 2 zone valves on some rads in a high rise apartment.We just took over this building and here is the problem.There are no isolation valves for the rad.The only isolation valves are at the risers which would cut heat off to 10 apartments. My question is there anyway to remove these valves without shutting down a whole wing of the building. I tried to talk landlord into waiting till spring.These rads are just in the bedrooms and they have lots of heat in the rest of the apartment. I figure as soon as i drain down a riser that is when all the problems will start,air locks etc. Any suggestions?