system won't hold air pressure to winterize
in the process of winterizing the system, I was blowing out each run with compressed air. i've done this every year for the last 8 years. in blowing out one line, I lost all air pressure and the system no longer holds any air pressure. I filled the system back up with water and there are no leaks. the house water meter shows no flow, no wet spots in the valve boxes or in the yard. could it be a faulty back flow preventer, a stuck open valve, a system leak? these all would have produced water flow when the system is filled with water.