Starting on the discharge side of a pump and moving outward, what components are used?

• A. A check valve, then a gate valve
• B. A gate valve, then a check valve
• C. Two check valves
• D. Check valve only

Answer: (A)

The main idea is to protect the pump from reverse flow while still giving you a convenient point to shut off the line for maintenance. Placing a check valve right after the pump prevents any backflow from the distribution system into the pump when the pump isn’t delivering flow. Putting a gate valve downstream (further along the discharge line) then gives you a means to isolate the discharge piping for service or isolation without removing the backflow protection. If you tried to put the gate valve first, you’d lose an effective, immediate protection against reverse flow at the pump, and using two check valves would be unnecessary redundancy. A single check valve plus a downstream gate valve provides both backflow prevention and clean isolation.