Hi Jon,

Depending on the age of the Conductivity probe, it may be giving false readings due to age. We typically see users swapping these probes every year or two. It ultimately depends on when the probe itself no longer holds calibration as long as it did when it was new. Before you go swapping it for a new one, I would suggest you re-calibrate.

- Make sure the 50mS calibration fluid is the same temperature of the tank water. You can leave the whole bottle floating in the sump for a few hours before doing the calibration.
- Use the primary temperature probe as the temperature compensation.
- When you are asked to enter the temperature of the fluid, enter the correct temp.
- Take the bottle out of the tank only when you are prompted to dip the probe in the 50mS fluid. This will eliminate the chance for the fluid temp to drop in-between calibration steps.

If you find that the probe ends up deviating from a reasonable value in short time, it may be best to replace the probe.