Nothing fancy here. A bunch of our business involves figuring out why a dry fire hydrant does not work. The often common story is that "it worked" when we installed it but now it doesn't and our investigative work reveals leaks at the suction head. And....often times that suction head was somewhat "homemade" from various pieces of pipe and fittings. The best practice is to design the system for minimum opportunity for air leaks. When using PVC components, this generally means just spend the money on a pre-fabricated suction head. Male or female thread is really your choice. They each have their own advantages and disadvantages...just be standard in what you do regionally.