Adding a Dedicated Irrigation Pump – Pressure Tank vs. VFD

Separating Irrigation from Household Water Supply

A homeowner wants to add a 220 V, 1.5 HP pump solely for a 12-zone irrigation system, currently fed by the house's 1 HP pump with a pressure tank. They prefer not to use a pressure tank for the new pump but worry about pump cycling on low-demand zones.

Options for Pump Control

• Pressure tank and switch: The standard, cost-effective solution. Set the differential as wide as possible (e.g., 30–50 psi) to minimize cycling.
• Variable Frequency Drive (VFD): Adjusts motor speed to match demand, eliminating cycling. However, VFD packages are expensive (often $1,000+) and typically overkill for residential systems.

Recommendation

Install a properly sized pressure tank (e.g., 20–40 gallon) with a standard pressure switch. It's reliable, affordable, and handles varying zone demands well. If budget allows and you want cutting-edge technology, explore VFD, but for most homeowners, the tank/switch combo is the practical choice.