the backflow preventer is located outside.
I'm planning to install this above the "T" leading to outside while the other end of the "T" leads down to the drain. So for servicing this master valve, I can just drain the water first.
I'm actually thinking of this setup that way my system is
"tamper proof" when the timer is off. The downside of this is that I will have to go to the basement and manually turning the system on if I have to do some testing...
Thanks for your feedback