A landscape contractor is performing a system audit on a large commercial property. During the audit, the contractor observes significant pressure variations across a single irrigation zone, with some heads misting and others barely spraying. The system was designed with a single large valve feeding multiple lateral lines. What is the most effective solution to address this pressure imbalance?
- AIncrease the main line pipe size to boost overall system pressure.
- BReduce the number of sprinkler heads on the affected lateral lines.
- CReplace all misting heads with higher GPM nozzles.
- DInstall a pressure-regulating valve (PRV) at the zone valve.
Show answer & explanationAnswer & explanation
Correct answer: D. Install a pressure-regulating valve (PRV) at the zone valve.
Significant pressure variations within a zone, leading to misting (too high pressure) and weak spray (too low pressure), indicate that the system is not operating at a uniform optimal pressure. A pressure-regulating valve (PRV) installed at the zone valve will reduce and maintain a consistent downstream pressure for the entire zone, ensuring that all heads operate efficiently at their designed PSI, eliminating both misting and weak spray.
Why the other options are wrong
- A. Increasing main line pipe size is for addressing overall system flow capacity or friction loss from the source, not for correcting pressure imbalances *within* a single zone that's already receiving water.
- B. Reducing the number of heads might increase pressure for the remaining heads, but it doesn't solve the underlying pressure imbalance and would alter the design coverage.
- C. Replacing misting heads with higher GPM nozzles would exacerbate the low-pressure problem for other heads and likely lead to more runoff.
Pressure Regulating Valve (PRV)
A type of valve that reduces a higher incoming water pressure to a lower, constant outgoing pressure, maintaining a consistent operating pressure for an irrigation zone or system.
- Essential for maintaining uniform emission device performance.
- Prevents misting, improves water distribution uniformity, and extends system life.
- Can be installed at the main line, sub-main, or individual zone level.
Memory trick: Pressure's wild swings? A PRV brings stable, proper things!