the big problem is when you want to work at different hieghts.
At cleantech a 2 man setup has 2 pumps, 2 controllers, 2 hosereels etc because its the only way to do it right.
If you do want to split your single reel to 2 poles, use a Y peice, and fit a valve to the pipe feeding the lower of the 2 poles, but not the higher one - this way you can restrict the lower pole to give the higher pole water, but you never choke the supply and cause it to cut off completely, or worse burn out a pump.