Water Well Pumping Systems

Pump-System Matching

The most efficient pumping system matches the pump performance curve to the system curve at the best efficiency point (BEP). An undersized pump delivers insufficient water; an oversized pump wastes energy and accelerates wear.

System Curve Components

• Static head (H_static): Vertical distance from water level to discharge point — constant regardless of flow
• Drawdown (H_drawdown): Additional lowering of water level during pumping — increases with flow rate
• Friction losses (H_friction): Energy lost to pipe friction — increases with flow rate squared
• Discharge head (H_discharge): Pressure at discharge point — constant for pressurized systems

Pump Performance Curves

Every pump has a manufacturer-provided performance curve showing the relationship between flow rate, head, power, and efficiency:

• Head-capacity curve: Shows maximum head at zero flow (shut-off) and maximum flow at zero head
• Efficiency curve: Bell-shaped curve — peak efficiency at BEP (70-100% of BEP for best performance)
• Power curve: Brake horsepower increases with flow — motor must be sized for maximum expected power
• NPSH curve: Net positive suction head required — must be available to prevent cavitation

Variable Frequency Drives (VFDs)

VFDs adjust motor speed to match demand — the single most impactful energy-saving technology for pumping systems:

• Energy savings: 30-50% reduction in energy consumption vs fixed-speed operation
• Soft starting: Eliminates water hammer — extends pipe and pump life
• Precision control: Maintains constant pressure regardless of demand variation
• Motor protection: Built-in overload, underload, phase loss, and ground fault protection
• Data logging: Records flow, pressure, power, and runtime for optimization

VFD Selection Criteria

Solar Pumping Systems

Photovoltaic-powered pumping eliminates grid dependence and ongoing energy costs:

• DC direct drive: PV panels → DC motor → submersible pump (simplest, most efficient)
• AC with VFD: PV → DC/AC inverter → VFD → AC motor (larger systems, more flexibility)
• Panel sizing: Array capacity = pump motor rating × 1.3-1.5 (account for temperature and orientation losses)
• Battery backup: Optional — provides pumping during cloudy periods or at night
• Float switch control: Turns pump off when tank is full — prevents overcharging

Multi-Pump Systems

For high-demand applications requiring redundancy and flexibility:

• Duty/standby: One pump operating, one on standby — automatic changeover on failure
• Duty/assist: Second pump activates during peak demand — staged operation
• Parallel operation: Multiple pumps sharing load — VFDs synchronize speed
• Cascade control: Pumps start/stop in sequence based on demand — minimizes cycling
• Lead-lag rotation: Alternates lead pump — equalizes wear across all pumps

Installation Procedures

Submersible Pump Installation

• Pre-installation: Verify well depth, casing ID, and water level — confirm pump fits
• Setting depth: Minimum 5-10 m below lowest anticipated water level
• Check valve: Install immediately above pump — prevents backspin and water hammer
• Discharge pipe: Use Schedule 80 PVC or steel — rated for system pressure
• Electrical: Submersible cable sized for motor HP and depth — use splice kit rated for underwater
• Torque arrestor: Prevents pipe rotation during startup — protects splice connections
• Pitless adapter: Underground discharge connection — prevents freezing in cold climates

Commissioning

• Flush system: Run clean water through piping to remove debris before connecting to distribution
• Verify rotation: Check motor rotation direction before lowering pump
• Measure performance: Record flow rate, pressure, and amperage — compare to pump curve
• Set pressure switch: Adjust cut-in/cut-out pressures for system requirements
• Program VFD: Set speed limits, pressure setpoints, and alarm thresholds