[SuperBK]

One small correction: Spikes should be plugged into the RELAY outputs, not digital inputs / outputs. The relay outputs can be reversed to reverse the spike, which actually allows it to control two solenoid valves. See the best practices document and the pneumatics manual.

relay1_fwd = 1; // turn on + side of spike
relay1_rev = 1; // turn on - side of spike

By wiring one solenoid to each side of the spike and the common of the solenoid to ground at the breaker panel, you can control both independently.

Brian