Diagnosing Gas/Air in a New Irrigation Well: Drawdown vs. Methane

Initial Symptoms

New irrigation well designed for 450 GPM at 85 PSI delivers only 250-300 GPM at 20-30 PSI. Air/gas visible at discharge. Pump set at 150 ft; drawdown to 115-120 ft at full flow—no cavitation.

First Theory: Excessive Drawdown (Ruled Out)

If pumping rate exceeds aquifer recharge, water level drops to the screen, entraining air. Test with a weighted bobber on a string: mark static level, run pump, measure drawdown. If drawdown reaches pump intake, that's the issue. But user confirms drawdown stabilizes well above pump—so not the cause.

Second Theory: Methane Gas Intrusion

With drawdown ruled out, the gas is likely methane—naturally occurring in some aquifers. Warning: Methane is explosive. This is a known but difficult well problem. Some pockets dissipate over time; others persist.

Possible Mitigation

• Consult multiple local well drillers—they've likely encountered this.
• Pump into an open pond/tank first, allowing gas to vent to atmosphere, then re-pump to irrigation. This adds cost but solves the gas issue.
• Size the second pump for irrigation demand; the well pump only fills the pond.

Next Steps

Contact the installing well company—if they guaranteed 450 GPM, they must remediate. Also test water for methane concentration. Don't ignore this; gas in the system damages pumps and poses safety risks.