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These pressure-actuated valves control the flow of the water to the nozzle(s). During bypass mode, all of the water is directed back to the supply; however system pressure remains constant (or slightly higher). This valve is typically used for applications which require frequent on/off action, such as a car wash application. However, they are more frequently used in applications that require a constant pressure at the point of use. They also are used whenever the driver of the pump is turned on/off, such as misting systems. While slightly different design concepts are used, typically these unloaders will actuate at 5 to 20% above the operating pressure of the system.

Flow ranges are from 0.5 GPM (2 l/min) to 625 GPM (2366 L/min) and pressure range is from 100 PSI to 50,750 PSI (7 to 3500 Bar). In lower pressure applications, a manually adjusted spring is used to control the flow; however, pneumatic and electric controls can also be used. Typical metal materials are forged brass, 303 stainless steel, 316 stainless steel and elastomers will be either Nitrile, Viton or Teflon.

For individual specifications see below.

WARNING: This product might contain a chemical known to the State of California to cause cancer, and birth defects or other reproductive harm. For more information go to

Specification US Metric
Minimum Flow2.1 GPM8 L/min
Maximum Flow66 GPM250 L/min
Min Pressure200 PSI14 bar
Max Pressure800 PSI55 bar
Maximum Temperature190 °F88 °C
Inlet Port1" BSP
Outlet Port1" BSP
Bypass Port3/4" BSP
Weight15.4 lbs.7 kg
The repair kits listed to the right are available for this pump. If you need further information about these repair kits, or have questions about other specific parts for your pump, please contact you local Giant distributor or contact Giant customer service.
Plunger Packing Kit – Part #09570
14 13247 Piston 1
15 13248 Seal Support 1
16 12021 Hexagon Nut 1
18 13012 O-Ring 1
20A 07281 O-Ring 1
21 07840 Support Ring 1
21A 13253 Support Ring 1
22 13254 Seal Pack 1
22A 13255 Seal Pack 1
23 13256 Valve Seat 1
25 12057 O-Ring 1
26 12055 O-Ring 1
28B 07653 O-Ring 1


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  • Giant Industries Limited Warranty
  • 22983R Literature


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