In manufactured parts, holes with female screw threads are often needed; they accept male screws to facilitate the building and fastening of a finished assembly.
2.
The tank itself has female screw threads for in and out; there are short male on both ends couplings that go into each; then, the female pipes that thread into those couplings end with like 6 inch stubs of copper pipe which are then soldered to the rest of the piping.
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