If a control tube to a hydraulic remote control valve in a sprinkler system ruptures, what will the valve do?

• A. Fluctuate between open and closed
• B. Remain in whatever position it is in
• C. Automatically close
• D. Automatically open

Answer: (D)

Hydraulic remote-control valves are piloted by a small control line. The pressure in that line acts on a diaphragm or piston to hold the main valve in a particular state, typically keeping it closed against a spring. When the control line ruptures, the pilot pressure is lost. With no pressure opposing the spring, the spring bias drives the valve to the open position, so water flows to the zone automatically. This is a fail-open behavior: loss of control pressure due to rupture causes the valve to open without any manual or electric signal.