Colorado Wastewater (WW) Operator D Practice Exam

When trying to stop reverse flow in a discharge line after the pump stops, you want a device that automatically blocks flow in the opposite direction. A check valve does exactly that. It allows fluid to move forward with the pump but closes automatically if the flow tries to go backward, so the discharge line isn’t drawn back toward the pump. Check valves come in types like swing checks and lift checks. A swing check uses a disc on a hinge that swings closed when reverse pressure appears. A lift check has a guided disc that lifts with forward flow and drops back to seal when flow reverses. Proper orientation and installation are important to ensure reliable closure. Other valves—the globe, ball, or butterfly—are primarily for isolation or throttling. They don’t automatically close to prevent backflow when the pump stops, so they don’t reliably protect against reverse flow on shutdown.