What is the purpose of a pressure relief valve in an irrigation system?

• A. To prime the pump when starting.
• B. To measure flow in the mainline.
• C. To release air pockets during drainage.
• D. To protect the system from over-pressurization by discharging water to atmosphere as needed.

Answer: (D)

The main idea is to guard the system against pressure spikes. A pressure relief valve is set to a specific pressure, and if the irrigation system pressure climbs above that point, the valve opens and vented water escapes to the atmosphere or a drain. This automatic release prevents excessive pressure from damaging pipes, fittings, valves, and sprinkler heads, and it also helps minimize water hammer when pumps start, valves close, or demand changes. It isn’t used to prime a pump, nor to measure flow, and air pockets are handled by an air release valve rather than a pressure relief valve.