I'd thought of thought too, but when I bought one from HD, the pipe threads just didn't seem right..Chink made of course.
Just didn't want to take a chance on cross threading the pumpm intake.
Some take NPT and others take MPT. So you have to be care ful on what you buy.
I got my one of my tees from Fastenal and it cost 2.99.
I talked to a local vac pump servicer and got my sizes straight before I took the plunge. You cross thread the the in take you are in for some expensive OEM parts