HDPE Barb sizing

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Im trying to educate myself how to purchase brass barb fittings to HDPE. My current project and forgive me for my lack of knowledge is a HDPE tube coming from my well from what i measured is 1-1/4 OD x 1" ID. To purchase the proper size barb for this HDPE pipe do i buy a 1-1/4 barb fitting or a 1" barb fitting?

 

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Pulled from Google
Hose barbs are sized by the tubing ID (inner diameter). So, the hose barb itself is going to be larger in diameter than the inner diameter of the hose. And that's what we're sizing for-- the inner diameter, the hose. For example, a 3/8 hose barb is 3/8 tubing ID.

 

[Sab Cek]

Im planning to replace the plastic extension barb to a brass barb coming from the well water supply pipe and wanted to reduce to 3/4 with pex just up to the 1" ball valve. The main reason reducing it to 3/4 is because i have 3/4 pex on hand. Is it ok to do that or should i just buy a piece of 1" pex and 1" stainless steel crimps?