plumbing pipe size

by William Bodnar
(Redlands,CA)

Are you supposed to step the size of the pipe down from the compressor to the drop downs. I have a shop with about 200ft of main air supply and 6 10ft drop down pipes. I had a old compressor from the 60s and out of the compressor had a 3/4 in pipe for the main then stepped down to 5/8 in and everything worked well. I am having a bran new compressor and dryier installed. out of the compressor and dryier looks lik 1/2 in pipe then it steps up to the 5/8 in pipe again. is this right?

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Bill says...

William... it's common for air lines to step down in size as the compressed air plumbing approaches the end application.

For example, with an air tool, it is often a recoil type air hose that is used, so the tool is moveable, and these are commonly sized smaller than the drop line.

The only downside to lowering the plumbing size is that you are restricting the flow of air somewhat. However, if you are feeding an air tool with a 1/4" inlet port with air from a 1/2" air line, you should not be concerned about the air supply being strangled by the plumbing.

My rule of thumb is to keep the compressed air pipe size as large as my budget and location will allow. Aside from cost, there is no down side to having larger rather than smaller air lines.

In fact, the main air line in many plants is 3" or 4" in diameter and that size of pipe, coupled with the long run, equals quite a nice supply of ready to used compressed air that doesn't, any more, have to travel all the way from the compressor to the point of use, each time the air tool is turned on.

Cheers,

Bill