What gauge wire should I use if my sprinkler valves are more than 700 feet away from the timer?

If the distance between the sprinkler timer and valves exceeds 700 feet (210 meters), you should use 16 gauge (AWG) wire for the connections. For distances under 700 feet, you can use Orbit sprinkler wire or 20 gauge plastic jacketed thermostat wire. (Page 6)