How do small ID connectors impact CFM/PSI?

by Bob

Air fittings

Air fittings

I am working on a basic 2 drop system for my 60 gallon single stage compressor (135psi, 12 CFM @ 90PSI, with a 1/2" output orifice). And I am getting hung up on pipe & hose sizing in relation to CFM & PSI.

1) How does having a 3/8" (.375") ID hose matter, when the factory 1/4" NPT fittings have an ID of ~.278"?

2) How is the CFM and PSI impacted by going from .375" to .278" then back to .375"?

I have read through a lot of content on your site this weekend, but still feel a bit uncertain about the impact of small orifices as the air moves between fittings (though I realize you have likely answered this even in something I have read already on your site). In my mind it seems like the small ID orifices would be a a bottleneck for air volume.

Thank you for all the time you put into sharing your vast knowledge of compressed air systems.

Comments for How do small ID connectors impact CFM/PSI?

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Aug 31, 2017
ID connectors - useless answer - REALLY?
by: Bill

I wonder if you actual read the page referred to in my earlier response, anonymous one?

Except for my ad in the top right column which is on every page on my site, there is nothing more on that page about selling a book.

The page is all about how you can estimate flow through orifice sizes, and how line size and plumbing affects flow, and references to in-depth calculations to help you navigate the sometimes minefield that is compressor and tool plumbing.

In other words, had you taken the time to look at the page, you'd have seen that the question was answered.

And if someone really wants an eBook about smaller air compressors, do buy mine!


Aug 30, 2017
Useless answer
by: Anonymous

Why not answer the question, I was not able to find a direct answer to this question which I have as well. I know you want to sell the ebook, but this simulator response here on many other questions makes this site far from useful. Good luck with your sales.

Mar 12, 2017
Air flow and air line flow pretty much covered
by: Bill , and many other flow related pages.

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