On Sun, 06 Jun 2021 14:24:30 GMT, Scott Lurndal wrote:
Pressurize it to three pounds below the cut-in presssure (e.g. 37#
if the switch is configured for 40-60).

Thanks for that information.

I'll set it at 27 psi given that the gray cap says the switch is a
"Pumptrol, SquareD, control circuit A600, Type FSG-2, Form U, class 9013,
Ser B, On 30, off 50" but I don't know yet how the air pipe connects to the
bottom.

Searching I think it's may be this one at Amazon
https://www.amazon.com/Square-9013-F.../dp/B00CONESDG

The pressure gauge might be this one
https://www.amazon.com/Brands2O-TC21.../dp/B000FKDLC4

I'm not sure how to find the bent brass piping though.