Starting at $107.00
  • Usually ships in 2-3 weeks



  • Flow Rate Settings: 0.5 GPM or 2.0 GPM
  • Port Size: 1/2" NPT, 3/4" IPS or 1" IPS
  • Primary Construction Material: Clear PVC
  • Max Operating Pressure: 120 PSIG @ 70°F; 50 PSIG @ 101°F
  • Max Operating Temperature: 120°F
  • Set Point Accuracy: ± 20%
  • Set Point Differential: 20% Maximum
  • Switch: SPST, 20 VA N.O. @ No Flow
  • Mounting Attitude: Vertical, Inlet Down


The Gems FS-400P series flow switches are designed for low cost/no-flow monitoring. Ruggedly constructed out of clear PVC, the transparent design is ideal for use where visual flow confirmation is desirable. These corrosion-resistant switches offer broad chemical compatibility. With only one moving part, their rugged construction offers long life with minimum maintenance. Ideal for water heating or purification, equipment cooling and general chemical processing use.

The FS-400P series is available with 1/2" NPT, 3/4" IPS or 1" IPS process connections with flow settings ranging from 0.5 to 2.0 gpm. The simple and reliable design is suitable for operating temperatures to 120°F and line pressures up to 120 psig. The FS-400P series utilizes a SPST switch.

Applications for the Gems FS-400P Series flow switch:

  • Protect Bearings or Gears: oil separators, fuel systems, pumps, compressors, presses
  • Electronics or Machinery: heat exchangers, semiconductor manufacturing equipment, induction furnaces, radio transmitters
  • Process Systems: water filtration and reverse osmosis, chlorinators, de-icers, sterilizers, evaporators


This product can be used in the following applications: