Carbon Dioxide pH control

CO2 pH Control Cabinet

Carbon Dioxide CO2 is a natural non-corrosive gas that can be used as a substitute for other acids (such as Muriatic acid HCl) in chemical treatment of pools and spas.

CO2 is available in standard pressurized gas cylinders. When dissolved in water, it forms carbonic acid H2CO3, a weak acid which can be used to lower the pH of water and neutralize liquid chlorine.


  • No handling of corrosive acid containers,
  • No corrosion of equipment and facilities from acid fumes,
  • No dangerous chemical reactions with chlorine,
  • Less danger of excessive low pH in water. Because carbonic acid is a weak acid, the lowest pH value that can be reached is 6.8, even under accidental runaway conditions.


  • CO2 increases the alkalinity of water and is therefore not recommended for applications where high alkalinity is a problem. Total Alkalinity (TA) should be maintained between 80 and 125 ppm.
  • High alkalinity increases acid demand, makes it difficult to lower the pH and may result in the formation of bicarbonate scale.
  • High alkalinity may be reduced with muriatic acid HCl or dry acid.


  • CO2 feeder cabinet ready for pH output relay connection of the CHEMTROL® controller,
  • Designed to control CO2-GAS flow, Inlet & outlet fitting connection with 1/4″ tubing,
  • Direct reading precision FLOWMETER with adjustable flow, 10-100 SCFH,
  • ASCO SOLENOID VALVE, brass body, 750 psi rating, 1/4″, 230V, 500r 60Hz,
  • PVC check valve, 1/4″ CO2 injector,
  • Feed tube & fitting 1/4″

* Recommended for industrial applications, as well as pools up to 2,250,000 litre (500,000 gallons)
** UL, NSF 50 and CSA Approved


Adjustable cylinder control or AUTOMATIC SWITCHOVER assures continued control of pH.


HARRIS 825 CO2 pressure regulator type 30 side inlet, adjustable 0-1000 kPa with 1/4″ tube fitting outlet.

Designed for Carbon Dioxide pressure control with rugged metal construction and large, easy to read colour coded gauges with safety seals.



AUTOMATIC CO2 SWITCHOVER SYSTEM, designed for 2 or more cylinders on the same feed line, one being kept on standby until the first one is empty.

The switchover automatically switches to the second cylinder when the pressure gets low. Additionally, more than one cylinder can be manifolded on each side of the switchover to further increase the CO2 supply.


The schematic illustrates the installation principle, showcasing the recommended optional Automatic Switchover System for continuous pH control assurance. Gas injection control is attained by connecting the 230v pH control output of the CHEMTROL® controller to the CO2 feeder cabinet.

Multiple CO2 gas cylinders can be manifolded together on each line to meet the required feed rate for maintaining proper pH levels.

Controller with co2 feeder set

For a clean and organized installation, it is recommended to mount the controller and CO2 feeder side by side on a PVC backboard with a thickness of 10mm. Incorporate slotted cable management ducting for a tidy arrangement. Assembly : grey PVC backboard 730×530 mm.