A.y. Mcdonald 3129-457 Pressure Switch 20-40 Psi 1/4 Npt

Product Description

The A.Y. McDonald 3129-457 is a water system pressure switch rated for a 20-40 PSI cut-in/cut-out range with a 1/4-inch NPT port connection. It monitors system pressure and signals the pump motor to start or stop, maintaining consistent pressure within a residential or light commercial water distribution system. The 1/4-inch NPT fitting allows straightforward integration into standard pressure tank piping. Licensed plumbers and pump service technicians are the primary installers of this device.

This pressure switch is suited for jet pump and submersible pump systems that use a bladder or captive-air pressure tank. The 20-40 PSI range is one of the most common factory settings for residential well water systems, providing adequate flow pressure for household fixtures and appliances. It is typically mounted at or near the pressure tank tee in the pump discharge line.

Key Features

• 20-40 PSI cut-in/cut-out operating range for standard residential well pump systems
• 1/4-inch NPT port for direct connection to standard pressure tank piping
• Automatic pump start and stop control based on system pressure
• Compact design suited for tight mechanical room installations

Compatibility

Designed as an OEM-style replacement pressure switch for residential and light commercial well pump systems requiring a 20-40 PSI operating range and a 1/4-inch NPT connection.

Installation Notes

Installation should be performed by a licensed plumber or qualified pump technician. Shut off electrical power to the pump circuit at the breaker panel and relieve system pressure before removing the existing switch. The NEC requires proper wiring terminations and appropriate circuit protection for motor-control devices. Do not energize the switch until all piping connections are secure and the system has been pressurized and checked for leaks.

Technical Specifications

• Pressure Range: 20-40 PSI
• Port Connection: 1/4-inch NPT

Standard Information

• Brand: A.Y. McDonald
• Manufacturer Part Number: 3129-457