I plan to replace a couple of bathroom radiators with towel ladders. The current rads have pipes coming straight up through the floor, and then valves/taps turning 90 degrees so that they enter the rad at its side. (Standard, modern Plumb Center fittings). All the towel ladders I've seen have entry/exit pipes at the bottom that are vertical. Does this mean I've got to remove the existing valves and fit the new rad directly onto the piping? If so, does that mean I've got to drain the whole system first? (If this sounds a bit basic, sorry!)