Diagnosing Pressure Drop in a Deep Well Irrigation System

A 310' deep well with a submersible pump at 163' feeds a zoned irrigation system directly (no tank). Spring startup pressure was 50 PSI; six weeks later it’s 40 PSI across all zones. The pump is 14 years old. The owner suspects a leak in the drop pipe or pump wear.

Key Observations

• Pressure drop is consistent across all zones.
• The pump pushes water up; a leak in the drop pipe would return water to the well, not lose prime.
• No visible surface leaks.
• Hard water (15 grains) may accelerate wear.

Troubleshooting Steps

1. Static pressure test: Pressurize the system, close the ball valve after the gauge, and watch for pressure drop. A rapid drop indicates a leak in the mainline or drop pipe.
2. Pump wear: At 14 years, the impeller may be worn, reducing efficiency. This is a common cause of gradual pressure loss.
3. Well yield: Unlikely to change in six weeks.
4. System changes: Confirm no new heads or larger nozzles were added.

Recommendation

Monitor the gauge. If pressure continues to decline, plan to pull the pump and inspect both the pump and drop pipe. Replacing the pump (and possibly the pipe) at 14–15 years is often economical given the labor involved. Hard water shortens lifespan.