Amp rating of the pump? Convert HP to amps if needed.... that will matter as to what wire size and breaker to use. You want to stay below a 3% voltage drop over a given distance, current and load....the longer the distance, the more resistance in the wiring which requires bigger gauge and breaker.

A 5 amp max draw from a pump would require #10 copper wire gauge and 30 amp breaker to stay below a 3% power drop from 220 volts over 500'

A 10 amp draw would require # 6 gauge wire and 55 amp breaker

Copper or aluminum wiring will matter as well since they differ in resistance values.

Voltage drop calculator....

http://www.southwire.com/support/voltage...

Hp X 746 Watts

---------------- = AMPS

Voltage

10 Hp Motor At 220 Volts

Is

10 Hp X 746 Watts

---------------------- = 33.90 Amps

220 Volts

Amps X Volts = Watts

First off you have not said what HP the pump is so how can anybody answer this. Go the Lowes or Home depot after you find out the amp draw of the pump and look at there wall chart. Or ask the supplier who you intend to purchase the wire from. Copper wire is to expensive to waste.

I'd use a double 40 and a minimum of 10ga . 500 feet is a long run .

10 gauge, 40 amp.