The dielectric of water at room temperature is close to 80. The firmware for the CWS655 is programmed to change volumetric water content to NAN when the permittivity measurements are greater than 42. When testing in water, look at the permittivity reading rather than the water content reading. If a test is being done for functionality, pull the CWS655 rods about halfway out of the water to see both permittivity and volumetric water content readings.
Note: The CWS655 was not designed for complete submersion in water. To conduct a water test, fully immerse the sensor rods in the water, but do not let the battery pack go under water.