Irrometer Watermark Electronic Module — WEM



The WATERMARK Electronic Module works in conjunction with a residential or commercial type irrigation controller to suspend irrigation when soil moisture status is appropriate for good plant heath. The included WATERMARK soil moisture sensors are placed in the root zone of the plant material being irrigated and wired to the WEM. The WEM can be used to manage a single valve, a group of valves (hydrozone), or the entire irrigation controller. When the controller attempts to activate irrigation, the WEM intercepts the signal and then interrogates the sensor for soil moisture status. If the soil is wetter than the set point, the system will prevent the irrigation cycle.


The irrigation system shall incorporate a soil moisture management device designed to integrate with the irrigation controller to suspend irrigation cycles based on soil moisture status. The soil moisture management device shall be comprised of two Granular Matrix Sensors (GMS) and an adjustable electronic control module. The module shall interpret sensor readings and prevent operation of the irrigation controller when soil is wetter than desired thresholds. The module shall have an eleven position switch to accommodate plant type and soil variances. The device shall be the WATERMARK Electronic Module as manufactured by the IRROMETER Company, Inc. of Riverside, California.

WATERMARK Electronic Module — WEM

  • COMPATIBILITY: The WEM is compatible with 24VAC irrigation controllers* that use a common ground. The module can be used in combination with other climatic sensors (rain, freeze, etc.).
  • *Note: The WEM is compatible with many two-wire and central control irrigation systems. Special order versions are available for dry contact switching and serial data output, contact IRROMETER for more information.
  • POWER REQUIREMENTS: Input voltage – 24 VAC
  • WIRE LEADS: 20 AWG x 12 in. (30 cm)
  • MATERIALS: 5 leads — 2 – sensor, 1 – power, 2 – switch/common ABS plastic case with encapsulated electronics for outdoor operation


  • HEIGHT: 3 in. (76 mm) – 3.875 in. (98 mm) including mounting tabs
  • WIDTH: 2 in. (51 mm)
  • DEPTH: 1.50 in. (38 mm) including knob
  • WEIGHT: .71 lb. (320 g) — total kit weight includes two #200SS-5 sensors
  • SETTINGS: OFF and 1 (wet) through 11 (dry)

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