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General Pump YU21405 Trapped Pressure Unloader with Green Spring - 4500 PSI

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2.68 lbs
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Brass body pressure unloader with 1/2 in. ports. 4,500 PSI maximum pressure.

Technical Specifications

Inlet Port: 1/2 inch
Max GPM: 21
Max PSI: 4500
Max Temperature: 200 degrees F

Product Description

4500 PSI Brass Pressure Regulation Unloader

The General Pump YU21405 pressure unloading device is made with highly durable brass and stainless steel. This unloader has 1/2" inlets, 1/2" bypass ports, and a 1/2" outlet. It is rated for a  maximum flow rate of 21 GPM and a maximum pressure rating of 4500 PSI. Maintain consistent pressure and protect yourself from dangerous spiking.


  • 21 GPM max flow rate
  • 4,050 PSI rated pressure
  • 4,500 PSI maximum pressure
  • (2) 1/2" NPT-F inlet port
  • 1/2" NPT-F outlet port
  • (2) 1/2" NPT-F bypass port
  • Brass construction
  • Stainless steel components
  • Green spring
  • 200° maximum temperature

Overall Dimensions:

  • 7.57" x 3.96" x 1.5"


The valve regulates the maximum pressure of the system by varying the flow discharged by the bypass. The adjustment is made by altering, by means of a piston, the position of a sphere which partially closes the bypass opening. The valve is sensitive to water flow. At gun opening, the water flows through the valve which maintains the system in pressure until the gun closes, the interruption of the flow provokes the complete aperture of the bypass which allows to discharge the flow at low pressure. At gun closure, the special mechanism of zero setting, which does not include a check valve, keeps in connection the delivery line and the bypass line, in that way permitting to lower the pressure all around the system and not only in the source line of the valve.


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