(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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Griffco Products - Back Pressure Valves

back pressure valves

NPI carries several products from Griffco such as Back Pressure Valves, Pressure Relief Valves and Calibration Cylinders. For more information, visit the sections for each product or Contact NPI.

Griffco diaphragm back pressure valves are designed to enhance the performance of chemical feed systems by providing a constant back pressure to the chemical feed pump, while also acting as an anti-siphon valve. Robust construction ensures reliability in the rigorous service of municipal and industrial applications.

Available in sizes 1/4" through 2".

Materials of construction include PVC, PP, PVDF, PTFE, 316 SS, Alloy 20, and Hastalloy C.


  • High Reliability / Low Cost
  • Robust, Machined Construction
  • Vulcanized PFA/EPDM Diaphragm
  • Externally Adjustable 0 - 150 psi
  • Anti-Siphon Function
  • Wide Range of Materials
  • Tamper Resistant Adjustment Screw
  • Manufactured and Stocked in the USA


Griffco diaphragm back pressure valves apply positive discharge pressure to a metering pump system to prevent siphoning and eliminate varying dosage rates caused by fluctuating downstream pressure. The diaphragm is held against the valve seat by an internal spring. When the preset pressure is exceeded, the diaphragm is forced up and chemical flows through the valve to the injection point. The valves are preset for 50 psi, however they are field adjustable from 0 - 150 psi via the adjustment screw. Installation should be as close to the injection point as possible to prevent chemical line drainage, and it is most important that all chemical system equipment such as pulsation dampeners and pressure gauges are between the pump and back pressure valve.

Pressure Relief Valves
Calibration Cylinders

If you don't see the specific information you are looking for on our website for Griffco you may go to Griffco's website at

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