Chloride water testing and sensor

What Chloride is and How to Test for it in Water

Chloride is a negatively charged ion that is formed when chlorine gains an additional electron. It is generally found in the form of salts, most commonly sodium and potassium salts, which are very soluble in water.

Aquaread Chloride Sensor

The Chloride sensor is an Ion Selective Electrode (ISE) that measures and tests for chloride ions in the water.


Key Features

  • Solid state ISE sensor.
  • Chloride Measurement range 0 – 20,000mg/l.
  • Chloride Resolution: two auto range scales: 0.00 – 99.9mg/l, 100.0 – 20,000mg/l.
  • Chloride Accuracy: +/- 10% of reading.
  • Simple to install on a wide range of Aquaprobes.
  • Sensor life of around 6 months depending on usage.
  • Long storage shelf life.

Our chloride sensors can be fitted on many of our probes - find some examples below.

To see all of the probes that feature chloride please visit the Products section



Advanced portable multi-parameter Aquaprobe.



The Aquasonde-2000 has 2 spare ports. They can house either 1x ISE sensor and 1x Optical sensor. Or it can house 2x ISE sensor.



Advanced portable multi-parameter Aquaprobe.

Solid State Sensor

Solid state sensors offer a significant advantage over gel-filled sensors offered by other manufacturers. Such gel-filled sensors have a limited lifespan, while solid state sensors like this one won’t deteriorate over time as long as it is dry.

Calibration and Temperature

Successful calibration of an ISE is fairly complex. On its initial use, a three-point calibration is required. Generally, this is at 10ppm and 100ppm of the sensor’s specific calibration solution, with the third point intended to characterise the effect of temperature on that specific sensor. The third point is a second calibration at 10ppm however, this calibration point must be at least 10 degrees colder than the initial point. This is because the measured concentration varies with temperature as well as the actual concentration of the ion.

The good news is that once this calibration is complete, subsequent calibrations do not require the third point to be re-done, making future calibrations much simpler to perform.


An ideal ISE sensor would only allow the ion in question to be passed through the membrane. However, in practice, all ion selective electrodes suffer from interference from ions which are similar in nature to the target ion. For this reason, ISE Electrodes are not recommended for use in brackish or salt water due to the high level of interfering ions.

Simple installation

Installing the chloride sensor into an Aquaprobe is a very simple process. Simply unscrew the blanking plug from an appropriate aux socket, apply some silicon grease to the thread of the sensor (grease provided), and screw in the sensor. After installation full calibration is required.