[Richard]

Jim, those devices are BOTH pressure regulator and pressure relief. They are extremely common on air compressors. In your case, if you decide to go this direction, the device would replace your pressure switch.

When the pressure reaches cutoff, the relays mechanically open, and at the same time an arm attached to the relays activates a simple valve that opens the line attached to it to atmosphere.

Newell used a system with an electrically actuated solenoid that drained the bottom of a water separator bowl. Fantastic in theory. The problem is the bowl on the separator is made of polycarbonate and eventually cracks and leaks badly.