Would 12ga on a 40amp single pole breaker work? 16.2amp makes it 12ga 2.5 x that for startup breaker 40amps?
Also, do you have a pump controller?
All it needs is a pressure switch. They are usually good to 2hp without a starter.
If this pump has a start winding(3wire with no ground or 4 wire with ground), it will most definitely need a controller/starter.
how would someone run a pump with a start winding without a controller that has a relay, capacitor and overload?
OP what wires does your pump have?
This is a shallow well pump. It has a regular motor. Capacitor, start switch all that is in the motor. All you need to do is turn the power on and off. Notice how the enclosure type is open drip proof and it has a standard frame size.
A submersible pump would need a pump control.
Good luck finding a 1 pole 40...
This is going on a dedicated circuit no matter what so just wire it for 240. 14 gauge wire on a 2 pole 20.