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685 Model Hydrostatic Liquid Head Indicator Switch: Full Line Overview

Installed and field calibrated in just minutes, as no intrusion into the tank is required. Add the optional Hi-Low switches for pump functions or alarm points, or even a 4 to 20 milliamp signal to give you complete control over your fluid levels.

The Series 685 Level Indicator operates by head pressure against the diaphragm which is transmitted by mechanical linkages to monitor and display local liquid levels onsite and remotely with the optional transmitter package.

Specifically designed for use in atmospheric (vented) tanks, standpipes, reservoirs, and similar vessels that in the past required strapping which exposed personnel to noxious fumes for monitoring liquid levels.

Featuring a +-2% level accuracy for tanks up to 60 feet tall, the Series 685 provides increased production and energy efficiency. The Hi-Low models are utilized to actuate valves or signal alarms.WellMark’s Multi-Switch model can contain up to seven switches for various level related system functions.

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685 Model Hydrostatic Liquid Head Indicator Switch: Full Line Overview


  • The Series 685 features an explosion-proof housing for added safety.
  • Vessel connections are available in an array of styles and materials.
  • Weather Proof Housing
  • Easy To Read Indicator Large dial face is easily read from your vehicle window. An optional remote monitor can be installed for even easier access to data.


  • Temperature Limit: 300˚ F
  • Accuracy: + -2%
  • Housing: Class I, Groups C & D; Class II, Groups E, F and G:
  • Rating: CSA Approved, LR-41663

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