Eliminating a section of baseboard radiator

Hey all, quick question. I have what I believe to be a monoflow radiant baseboard heating system. I took a look at the piping under the house, and there's a large main line and the radiators seem to be connected to that by smaller copper lines. What I have is a baseboard unit on a corner, and what I want to do is eliminate one ell of that corner. In the monoflow system, can I simply turn the valve off at the supply side of that radiator and then remove what I want to, or do I have to drain the entire system?