A German-made reciprocating triplex plunger pump.

Spheroidal cast iron crankcase with sight glass and vented dipstick; forged, through-hardened, ground and polished crankshaft; bronze connecting rods; hardened stainless steel plunger bases; solid ceramic plungers; nitrile seals with fabric reinforcing; stainless steel valves and nickel-plated spheroidal cast iron manifold.

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

  • GP5128 Exploded View
  • GP5128 Parts List
  • GP5128 Torque Specifications
  • GP5128 Technical Drawing
  • Giant Industries Limited Warranty
  • GP5128 Installation Instructions
  • GP5128 Repair Instructions
  • Troubleshooting Guide


U.S. Metric
Maximum Flow 20.6 GPM 78.0 L/min
Maximum Discharge Pressure 4060 PSI 280 bar
Crankshaft Speed 1000 RPM
Power Consumption 57.7 HP 43.0 kW
Maximum Inlet Pressure 145 PSI 10 bar
Maximum Temperature 140 °F 60 °C
Plunger Diameter 1.1″ 28 mm
Stroke 1.81″ 46 mm
Crankshaft Diameter 35 mm
Crankshaft Rotation Top of Pulley Towards Manifold
Crankshaft Mounting Either Side
Inlet Ports (3) 1-1/2″ NPT
Discharge Ports (2) 1″ NPT
Crankcase Oil Capacity 1.21 gal 4.6 L
Weight 179 lbs. 81 kg
Key Component Material
Manifold Nickel-Plated Spheroidal Cast Iron
Plungers Solid Ceramic Oxide
Valves Stainless Steel
Seals Nitrile with Fabric Reinforcing
Gear End Spheroidal Cast Iron

Click the image to enlarge


RPM GPM 1000 PSI 2000 PSI 3000 PSI 4060 PSI
600 12.4 8.6 17.1 25.7 34.7
700 14.4 9.9 19.9 29.8 40.3
800 16.5 11.4 22.8 34.1 46.2
900 18.5 12.8 25.5 38.3 51.8
1000 20.6 14.2 28.4 42.6 57.7

Horsepower Requirements

The ratings shown are the power requirements for the pump. Gas engine power outputs must be approximately twice the pump power requirements shown above.

We recommend a 1.15 service factor be specified when selecting an electric motor as the power source. To compute specific pump horsepower requirements use the following formulas:

Electric HP = (GPM X PSI)/1450

Gas HP = (GPM X PSI)/1100

*Engine power varies based on horizontal or vertical orientation, as well as by makes and models from each manufacturer.


Plunger Packing Kit – Part #09761
35B 08183 O-Ring 3
36 13228 Grooved Ring 3
37A 07700 O-Ring 6
40 13115 V-Sleeve 6
Valve Assembly Kit – Part #09762
46 07060 Valve Assembly 6
48B 13012 O-Ring 3
Oil Seal Kit – Part #09230
31 13284 Oil Seal 3

Repair Kits Available

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.

Service & Repair

Giant provides service on each pump and accessory that we sell. Many basic repair procedures are covered in the Giant repair manual. For all other questions on service or repair needs please contact your local Giant distributor.