(800) 378-1500
285 Portsmouth Ave. Stratham, NH 03885
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The Building Blocks for Water Treatment Equipment

“Everything but the Chemicals”

Northeast Pump and Instrument (NPI) specializes in the design, sale, installation and repair of chemical feed equipment, systems and instrumentation for water and wastewater treatment. Our involvement in the industry spans more than 30 years and our technical staff boasts over 100 years of combined industry experience.


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Calibration Cylinders

back pressure valves

Griffco calibration cylinders are designed to enhance the performance of chemical feed systems by providing a verification of the flow rate of the chemical feed pump.

Robust construction of clear PVC with an easy to read graduation in mls and gph.

Available in three models: EZ-Clean, Vented, and Open Top.

Available in six sizes: 100 mL, 200 mL, 500 mL, 1000 mL, 2000 mL, 4000 mL, 10,000 mL, and 20,000 m



  • High Reliability / Low Cost
  • High Contrast Graduation Markings
  • Clear Easy-View Tube
  • Robust Construction
  • Direct GPH Readout
  • Sealed Top with Overflow Connection
  • Optional EZ-Clean Model
  • Optional Open Top with Dust Cap


Griffco calibration cylinders are installed in the suction line to the chemical metering pump. Two isolating valves, (not supplied) must be installed in the suction line. The top of the cylinder should be vented back to the storage tank or to drain. Fill the cylinder to the top mark then close the valve from the chemical tank. Switch on the chemical feed pump and draw down the chemical in the cylinder for 30 seconds. Switch the pump off. The reading on the left side of the cylinder is a direct readout of USgph. Alternatively, observe the volume withdrawn on the ml scale. To convert to LPH or GPH use this formula.

LPH = (volume/draw time) x 3.6
GPH = (volume/draw time) x 0.952

(800) 378-1500
285 Portsmouth Ave.
Stratham, NH 03885