hey, The backflow you want before your sprinkler valves. So i guess they would install your tanks run up a pipe, put in the backflow and in the sprinkg you would tap off of that. As far as the winterization, simply install a tee, before the backflow, and cap it off. (normally its 1/2" female threads on the tee, capped with a 1/2" threaded plug) then you attach the compressor to there. i would suggest having a professional winterize your system unless you have a sufficent size compressor, that way there are no flaws. Winterizing is a crucial step to the life of the system
Thanks
Ray
Rays Above and Beyond Automatic Lawn Sprinklers