CH265 pH / Free Chlorine Digital Controller


CHEMTROL® CH265 PPM/pH Digital Controller introduces the new PPM Sensor for Free Chlorine control. A microprocessor-based digital controller, designed to maintain both free chlorine (PPM) and water pH in Municipal Water, Well Water, Waste water and Industrial applications.

  • No Reagents
  • No Maintenance
  • No Pressure Regulator.
  • Free CL Range 0.00 to 10.0 PPM
  • pH Range 0.0 – 14.0
  • Programmable 4-20 mA output to PID and/or Chart Recorder
  • Programmable 4-20 mA Output Control with Adjustable Setpoint
  • Dry Contact Remote Alarm


  • Easy to install
  • Simple to use
  • All Control Functions on Front Panel
  • Separate Adjustable Setpoints
  • Separate Adjustable Alarms
  • Acid/Base Selector
  • Proportional Feed with Adjustable Bandwidth
  • Separate Adjustable Overfeed Safety Timers
  • Rain and Splash Proof Cabinet
  • 5-year Electronics Warranty


The new Free Chlorine Sensor is a solid state sensor with a selective membrane that provides direct readings of Free Chlorine in water at concentrations ranging from 0.1 to 10 ppm (parts per million) or mg/l (milligrams per litter). These are true readings of Free Chlorine corresponding to the DPD #1 test.

A significant advantage of this PPM sensor is that it’s not affected by cyanuric acid (CYA) stabilizer and/or oxidizers, thereby assuring constant Free Chlorine levels at all times. Unlike other chlorine sensors on the market, this new sensor is easy to install and maintain and gives the operator precise and reliable control of Free Chlorine under the most difficult conditions. The PPM sensor is covered by a full 2-year warranty.


FREE CHLORINE CONTROL Adjustable from 0.1 to 10.0 ppm (mg/l) or 0.01 to 3.00 (specify)
pH CONTROL Adjustable from 0.0 to 14.0
FREE CHLORINE SENSOR Solid state electrode with 3 m cable
pH SENSOR Glass electrode with 3 m cable
READOUTS PPM (3 digits) and pH (2 digits) LEDs
FEED MODES Manual, automatic, proportional
ADJUSTMENTS Set-point, calibration, limits, feed rate
INDICATORS LEDs for feed mode, feed status, alarms
4-20 mA Output Out-of-range limits
CABINET Polystyrene 22 x 18 x 10 cm
ELECTRICAL 230V or 24 VAC (specify)
PLUMBING Flow Cell Assembly with Y-Strainer
WARRANTY 5 years on electronic module
1 year on all other parts
SHIPPING 30 x 30 x 30 cm carton, 3 kg without pumps
6 kg with 2 chemical feed pumps


Unlike conventional amperometric or colorimetric sensors, the new PPM sensor is easy to install and maintain. It does not require a pressurized cell for the sensor and/or expensive and expendable chemical reagents. And best of all, it’s maintenance free.

Installation of the CHEMTROL® 265: For best operation, it is recommended to install the sensors on a bypass line with a Flow Cell Assembly (FCA) as shown on the schematic.


The Flow Cell Assembly (FCA) includes a see-through cell with a plastic cover that regulates the flow of water and allows the operator to see the tip of the sensors.

The cell includes the following:

  • Two 1/2″ FPT fittings for the connections to the bypass line
  • Two 1/2″ FPT fittings for mounting the sensors
  • A spigot for water testing
  • A bleed line to prevent air lock in the cell

In addition it is also recommended to install a safety switch on the bypass line to prevent accidental feeding of chemicals.


The CHEMTROL® 265 Free Chlorine Analyzer automatically maintains both Free Chlorine concentration and pH of the water.

All operating functions are clearly labelled and accessible from the front panel, with safety and easy-reset features not found on other controllers.

The Free Chlorine concentration can be adjusted from 0.0 to 10 ppm (or mg/l) based on local Health Department regulations for prevention of germs and bacteria (or from 0.01 to 3.00 for low chlorine level applications).

The pH control level can be adjusted from 6.0 to 8.0. Below 6.0, the water is too acidic and causes corrosion. Above 8.0, it is too alkaline and causes scaling, stains and reduced sanitizer efficiency.