Upgrading compressor fittings?

by Michael
(San Antonio, Texas)

Upgrading fittings from 1/4" (1/4"NPT) to 3/8" (1/4"NPT) and using 3/8" hose (1/4"NPT).


Just purchased CP 10 gal air compressor #62441. I would like to upgrade the fittings to 3/8" (1/4" NPT). I have my shopping list almost complete, but I do not know the size of the quick connect that is already attached to the air compressor. Do I have to switch it out with a 3/8" coupler (1/4"NPT) also? Just trying to maximize the air flow.

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Jul 30, 2018
Upgrading compressor fittings
by: Bill

Michael, I've moved your question to the fittings forum as it's appropriate for all makes of air compressors.

A 1/4" air hose (remember, hose is measured on the I.D., not the outer diameter) moves a massive amount of air.

Nevertheless, it's rarely a problem to upsize the fittings, couplers, connectors and air line if desired.

The NPT sizes you show in your question confuse me a bit, as they all say 1/4" NPT even though you refer to different sizes.

See the NPT size chart on this site to compare the ACTUAL hole sizes represented by the NPT sizes. In all cases, the actual hole size is much bigger than the fraction 1/4" or 3/8" might suggest.

Now, back to your question.

When you say you don't know the size of your coupler, you are referring to the thread size, yes? Just measure the thread and compare it to the NPT chart.

If you are referring to the connector size, it's shape will remain constant though the hole size, and corresponding connector size, may get bigger. Any connector that fits that coupler now will work, and if you get a bigger coupler and connector that fits that bigger coupler will also work, though you may need to add a bushing or adapter to connect it all together.

Every time you put a fitting or a coupler in the air line, you reduce air flow. So, upsizing the coupler would help increase the air flow through that coupler. But them, you would have to upsize all the connectors, both in the air line and the air tool, otherwise, a downstream smaller connector become a choke point.

Having said that, it depends on what you are trying to drive with compressed air and the flow requirements of that air tool that should help you decide.

Running a grinder or the like? More air flow is better. Driving a nailer with air, higher flow is rarely necessary as this is typically a "one shot" air user, versus a grinder that eats compressed air continuously.

Hope this helps. If I've confused you or if you have more questions, add a comment, please.

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