For the system to work you have to raise the hole loop. If you just raise part of it you will not be able to get all the air out of the system. Keep in mind that all lines should pitch up to your radiators, any traps in the line will hold air and not allow the water to circulate. Be sure to install the copper tees in the same location as the existing tees. It's been a long time since I installed a system like this. If my memory serves me right the tees must be more then 18" apart and no closer then 18" from a change of direction in the main. Also keep in mind that the monoflow tees are directional. There are arrows in the tees that must point in the direction of flow.