Removing anti syphon valve backflow preventer

Removing an outside residential home anti-syphon valve backflow preventer using some common tools; dremel with grinder wheel, small drill, small drill bits, no. 2 easy out, small crescent wrench, wire brush, small hammer, center punch and something solid to buck up against the hose spigot while cener punching and drilling.
My set screw thread length was 1/4"-drill only 3/4 of that which is about 3/16" and no more otherwise you will damage the threads on the hose spigot.
If you plan to use another new anti-syphon valve-don't screw the setscrew so tight, use some graphite grease on the threads and a stainless steel allen set screw would be good so you can take it off again. My set screw size was; Metric 5 X 0.80 X 5 MM.
Now of course when your using a metric screw you'll need some small metric allen wrenches. Not sure which one though.
Thanks for watching.