Electricide Chlorine Dioxide Systems

Ozone Bottled Water Disinfection Systems

Fiberstrut Channel and Fasteners

ProMinent Chemical Dosing Equipment

Fristam Stainless Steel Hygienic Pumps

Atlantium HOD UV Disinfection

Glasco UV

LSM Pumps Hose Pumps

Likuid Nanotek Ceramic Membranes

IPM Systems Powder Feed Systems

Chemical Dosing Systems

Ozone Systems

Chlorine Dosing Systems

Sodium Hypochlorite Dosing Systems

Gas Chlorine Dosing Systems

Chlorine Dioxide Dosing Systems

Electrochemical Generation Systems

Acid Chlorite Generation Systems

UV Disinfection Systems

Chemical Dosing Systems

Building Mount Dosing Systems

Skid Mount Dosing Systems

Fluoride Dosing Systems


Chemical Dosing Systems ProMinent Ozone Chlorine Dioxide UV CircleClear Backwash Recovery Sodium Hypochlorite Aickinstrut Fiberstrut

us flag 

United States Office

aust flag 


United States

P: 702-938-6418  F: 702-938-4118
Suite B-562 / 2654 W Horizon Ridge Pkwy
Henderson NV 89052-2803

Sydney (NSW)
P: +612 9999 4594  F: +612 9999 4534
Unit 9, 5-7 Prosperity Pde, Warriewood NSW 2102 Australia
Perth (WA)

P: +618 9337 5415  F: +612 9999 4534
Melbourne (Vic)

P: +613 9005 1681  F: +612 9999 4534



Chemical Dosing Systems




Dioxide Pacific

What is Chlorine?

Chlorine is a gas at room temperature and pressure and is soluble in water. Chlorine hydrolyses with water to form hypochlorous acid and hydrochloric acid according to the following equation:

Cl2 + H2O → HOCl + HCl

Sodium Hypochlorite reacts with water as follows:

2NaOCl + H2O → NaOH + NaCl

This hydrolysis feature makes chlorine very suitable for water disinfection applications where turbulence is present, as chlorine is not present in water as a dissolved gas like chlorine dioxide or ozone.

How is Chlorine Available?
Gas ChlorinationChlorine is commercially available as a liquified gas in 70kg cylinders or 920 kg drums.
Sodium hypochlorite is available as a 12.5% solution or 10% solution (depending upon location).
Calcium hypochlorite tablets and granules are sold in 10kg and 50kg buckets. The tablets and granules contain 65% available chlorine.

Gas ChlorinatorGas Chlorine Dosing
Gas chlorine is safely dosed from cylinders or drums using remote vacuum gas chlorination equipment. The vacuum regulator (the heart of the chlorinator) is mounted directly on the cylinder isolation valve using a lead gasket. Chlorine gas under pressure is fed to the inlet pressure reducing valve, the needle of which is seated on a diaphragm. At the water end of the system, pressure differential is applied across a venturi by a boost flow which causes the venturi to suck. This vacuum is applied to the diaphragm, causing the needle to be  pushed into the spring loaded valve, thereby allowing chlorine gas to flow into the chlorinator. Gas chlorine under vacuum then proceeds through a flow regulating device (needle valve V notch) and through the vacuum tube to the venturi where it is dissolved in water.

The key feature of the gas chlorination system for water disinfection is that it operates completely under vacuum and is therefore inherently safe. If the booster pump stops or the venturi becomes blocked or the vacuum tube is broken, vacuum is lost at the chlorinator. The inlet pressure reducing valve immediately closes and the cylinder or drum is completely isolated. Even if the cylinder was to fall over and the body of the chlorinator was to smash, the inlet pressure reducing valve would still stay closed and no chlorine gas would escape.

Gas chlorination can occur from 920kg drums. Chlorinators are equipped with a drop leg and heater where any liquid chlorine is vaporised. Normally, this is only required for connection of the drum immediately after transport. After a short operation time, the heater is not required but is normally left on.

Gas chlorination systems are usually supplied as duty-standby units so that chlorine gas is continuously available for water disinfection. Change-over from the duty cylinder or drum to the standby unit is via a vacuum shuttle valve. When the cylinder is empty, vacuum increases to such an extent that the valve shuttle is pulled over to the other side, allowing the standby cylinder to come on line.

sodium hypochlorite metering pumpSodium Hypochlorite Dosing
Sodium Hypochlorite is supplied as a 12.5% solution and is readily available in 20L drums, 200L drums and tanker loads for larger installations. Chemical storage tanks are usually manufactured from polyethylene. Sodium hypochlorite is dosed with solenoid operation dosing pumps or motor driven metering pumps.

12.5% sodium hypochlorite undergoes gasification as it decomposes to give off oxygen gas. This gasification can cause problems with chemical metering pumps as the gas will accumulate in the metering pump suction line, eventually making its way into the liquid end where loss of prime is the result. The ProMinent Gamma/L and Beta dosing pumps have solved this problem with the specially designed auto-degassing liquid end. Gas is removed from the suction line through a vent valve and directed back to the storage tank with a small amount of liquid. The clear chemical is then dosed through the discharge valve.
Larger metering pumps (>20 L/hr) don’t usually suffer from loss of prime as the valves are much larger and the volume of chemical being pumped is also larger.

Suction connections between the bulk sodium hypochlorite storage tank and the metering pump should be designed to minimise formation of gas pockets. A calibration cylinder immediately prior to the metering pump will function as a gas accumulator and allow gas to rise and vent off. If the suction line is run downwards from the tank to the pump, gas will rise back into the tank.

One way to prevent gasification is to dilute the 12.5% solution to 1% using potable water. Although the metering pump will have to be 12.5 times larger, the 1% solution will last decay approximately 144 times slower than the concentrated solution.

Definition of Strength
Five common definitions of sodium hypochlorite solution strength are as follows:

  • Grams per litre of available chlorine = The weight of available chlorine in grams in 1L of sodium hypochlorite solution. This is determined by analysis.
  • Grams per litre of sodium hypochlorite = 1.05 x grams per litre available chlorine.
  • Trade percent available chlorine = grams per litre available chlorine/10
  • Weight percent available chlorine = grams per litre available chlorine/ (10 x sg)
  • Weight percent sodium hypochlorite = weight percent available chlorine x 1.05

Chlorine Residual AnalyserMeasurement of Chlorine Residual - Chlorine Residual Analysers
ProMinent is the largest manufacturer of chlorine residual measurement probes in the world. Chlorine us measured using the amperometric principle with a closed cell utilising electrolyte and a membrane cap. The membrane cap selectively allows chlorine species through to be measured. There are different probes for measurement of either free chlorine or total chlorine. All probes do not require continuous addition of buffer, are simple to operate and easy to calibrate. The zero point of each probe is electrically stable at 4mA due to the constant pH and conductivity of the electrolyte solution which encapsulates the electrodes. The probe electrodes don’t come into contact with the water so only the membrane cap needs to be replaced if it becomes fouled. Other competitor units have open electrodes which contact the water. These electrodes become fouled and the zero point changes as the pH and conductivity of the water changes.

Typical chlorine residual analysers are supplied on wall mount backboards, pre-wired and pre-plumbed. The controller will feedback control any system such as a gas chlorinator, dosing pump or cal hypo feeder.

Safety Issues
Gas chlorine has very stringent storage and handling requirements in all countries as chlorine gas is toxic. A chlorine gas leak is to be avoided at all costs. Usually trained operators are comfortable handling gas chlorine and there have been comparatively few incidents, considering how widespread it is used. Cylinders or drums are to be stored in a lockable area, and unauthorised access prevented. The room and the dosing area should have a chlorine gas leak detector installed which will activate an alarm and shut the system down. The Dioxide Pacific ProGuard automatic cylinder shut-off device will immediately turn the cylinders off if a leak is detected.

Sodium Hypochlorite is a dangerous good and has the issue that a splash can cause blindness. Transfer of chemical from bulk tankers is to be done without operator intervention using appropriately designed systems. Transfer of small quantities (20L or 200L) can be done with a Dioxide chemical transfer system and there will be no operator contact.

Calcium hypochlorite tablets are not a major safety concern except that they should not be heated or put in contact with oxidisable substances

Please contact us for further information on chlorine water disinfection systems.

[Home] [Products] [Systems] [Contact  Dioxide Pacific]