Chemtrol a Division of Santa Barbara Control Systems

- Model 265 - pH Free Chlorine Analyzer



The CHEMTROL265 PPM/pH Digital Controllerintroduces the new PPM Sensor for Free Chlorine control in automated water treatment. A microprocessor-based digital controller, it is designed to maintain both free chlorine PPM and water pH in high-end residential pools, small commercial pools and spas and light industrial applications. Unlike other chlorine sensors on the market, these sensors are easy to installl and maintain, very precise and so reliable that they are covered by a full 2-year warranty. For better water management results, it is recommended to use ORP control of chlorine oxidizing activity and PPM monitoring of free chlorine. Alternatively, PPM control can be used for control of the sanitizer and ORP control for an oxidizing agent, such as ozone.

with True Free Chlorine Control and 4-20 mA outputs

An easy-to-use advanced controller for:

  • Municipal Water
  • Well Water
  • Industrial Water
  • Waste Water.


  • No Reagents.
  • No Maintenance.
  • No Pressure Regulator.
  • Free CL Range 0.00 to 10.0 PPM.
  • pH Range 6.0 - 8.0.
  • Programmable 4-20 mA output to PID and/or Chart Recorder.
  • Programmable 4-20 mA Output Control with Adjustable Setpoint.
  • Dry Contact Remote Alarm.


The new PPM Sensor for Free Chlorine 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 liter).

These are true readings of Free Chlorine corresponding to the DPD #1 test.

A significant advantage of this sensor is that it's not affected by cyanuric acid (CYA) stabilizer and/or oxidizers, thereby assuring constant Free Chlorine levels at all times. Extensive laboratory and field tests have shown it to be very accurate and reliable.


The CHEMTROL®265 Free Chlorine Analyzer incorporates advanced communications capabilities, including:

  • Wireless
  • Ethernet
  • Internet
  • Dial up Modem
  • Direct Comport
  • RS485
  • Mod Bus

  • 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
  • Toll-Free Technical Support

Each controller is supplied with a detailed 12-page instruction manual and a FIVE-YEAR electronics warranty.

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.

For best results, it is recommended to use the CHEMTROL® FLOW CELL ASSEMBLY (FCA) on a bypass line as shown on the schematic.

The 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:

  1. two 1/2' FPT fittings for the connections to the bypass line,
  2. two 1/2' FPT fittings for mounting the sensors,
  3. a spigot for water testing,
  4. 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.


Technical support from CHEMTROL® is based on our experience with over 30,000 installations worldwide since 1976. It is also available by toll-free phone, by fax or by e-mail.

The CHEMTROL® 265 Free Chlorine Analyzer is based on 25+ years of experience in water treatment with over 25,000 installations worldwide. Featuring a 5-year electronics warranty, it actually pays for itself in 1 to 2 years through cost savings in operating and maintenance expenses.

Savings continue to accrue from the more efficient use of chemicals, avoiding over- and underfeeding, and from lower labor costs for water testing and repairs of damaged equipment.

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