Apollo Backflow preventer valve Air Purge Plug

I was trying to blow out my sprinklers for the winter but noticed that my backflow valve was fluttering the whole time I was trying to purge the sprinklers instead of sealing like it does with water. To prevent the backflow valve from being damaged by the fluttering, I made this backflow valve cap that fits into the same threaded top of the Apollo backflow valve. I recommend removing the spring and valve assembly by simply lifting them out of the unit prior to installation of the cap. This also ensures that there isn't any water that could freeze stuck in the spring assembly of the valve. This cap fits snuggly and kept all of the air from my compressor headed down to the sprinkler heads instead of leaking out the top of the backflow valve or damaging the valve by fluttering during sprinkler winterization.