Compressed-Air-Sprinklers

This page relates to blowing out sprinkler lines.

In blowing out the lines of compressed air sprinklers, usually it's the volume of air and not the pressure that does the trick.

While I'm not a physics major, it seems to me that damage to a sprinkler pipe occurs when that pipe remains full of water during the cold winter months, and then the water freezes.

Water expands as it freezes, and if the there's no place for the forming ice to go, it's powerful enough to rupture the sprinkler pipe.

If you're blasting air into the sprinkler lines at the highest point in the sprinkler line, I would think that as long as there's nothing but mist coming out the other end - after all the free water that had been filling the pipe had been blown down to and out of the outlet - then any small amount of water in the lines shouldn't present a freezing hazard.

See the math just below.

Here's the math!

Thanks to Mike Higgins of Grand Junction Pipe & Supply in Grand Junction Colorado who tells us…

“The following equation should be used to figure out the proper volume of air needed for your system.

The size of the compressor needed should be based on this equation.

This is based on Cubic Feet per Minute (CFM’s) and the Gallons Per Minute (GPM’s) for which your system is designed.”

If you take the GPM of your system, and divide it by 7.5 it equals the CFM you’ll need to push the water out.

Mike goes on to say that if your system flows 20 GPM of water at 30 PSI, then you divide the 20 GPM by 7.5 to get the CFM necessary to adequately blow out your lines. In this case the answer is 2.66 CFM, so you’ll need a compressor able to provide that flow of 2.66 CFM at 30 PSI to get all the water out or a reservoir with enough volume of air already compressed to generate that flow.