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General Pump ZK51 Flow Sensitive Unloader, 1450-2900 PSI, 3.0 - 4.2 GPM

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3.00 lbs
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Flow-sensitive unloading valve with pressure adjusting screw, protecting your system from overpressure. Stainless and brass internal parts. 3.0 to 4.2 GPM, adjustable pressure from 1450 PSI to 2900 PSI.

Technical Specifications

Max GPM: 4.2
Min PSI: 1450
Max PSI: 2900
Max Temperature: 165 degrees F
Inlet Port: 3/8 inch
Outlet Port: 3/8 inch
Bypass Port: 3/4 inch
Min GPM: 3.0

Product Description

General Pump Flow Sensitive Unloader

The General Pump ZK51 flow sensitive unloader features a flow-through design, protecting your system from overpressure and spikes. Stainless and brass internal parts for durability, no external moving parts or springs for ease of use and reliability. Eliminates high pressure in all lines while unit is in bypass mode while also eliminating pressure peaks normally generated by conventionally designed unloaders. Unique balanced piston design permits precise pressure adjustment. Easy to maintain and service. Dual gauge ports - always use a pressure gauge when making adjustments! Best for single pump or Non weep guns.

Valves require a minimum of 5% by-pass at ALL times.

Dimensions: 6.31" x 4.00" x 2.75"


  • Volume Range: 3.0 GPM - 4.2 GPM
  • Pressure Range: 1450 PSI - 2900 PSI
  • Inlet Port: 3/8" NPT-F
  • Bypass Port 3/4" MPT-M   
  • Outlet Port: 3/8" MPT-F
  • Max Temperature: 165°F

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