How To Bleed Air Out Of Sprinkler System Fire Sprinkler Head - How To Bleed Air / Disassemble?

Fire sprinkler head - how to bleed air / disassemble? - how to bleed air out of sprinkler system

He was living with my-water system that has a sprinkler system with heads of the joint cabinet drain. Do you need to change the water again. I looked in the manual air bleed from the top and head irrigation system further. How exactly how to do it? He lifts his head with a wrench? You may have to be solved easily? Or maybe turn the baffle or loosen it makes, so that opening the valve partially? I do not want to mess up.

In addition, I have attached drywall on the ceiling in one room, the unfinished trailer eschutcheon head hanging. What is the best to achieve this practice?