2903 W. Whitton Ave, Phoenix, AZ 85017
P.O. Box 27296, Phoenix, AZ 85061-7296
602 650-1557 / 800 443-6936


Gas Chlorination System Sizing

The selection of a gas chlorinator is dependent upon the flow rate of water to be treated, in Gallons Per Minute (GPM); and the chlorine demand of the water, in Parts Per Million (PPM). The feed rate of the chlorinator is expressed in Pounds Per Day (PPD).

Chlorine demand is the tendency of the water you are treating to consume the chlorine that you mix into the water. Chlorine demand in your water is effected by many different things. Some of them may be: algae, bacteria, iron, manganese, hydrogen sulfide, water temperature, and agitation, or aeration, of the water. While it is possible to test for chlorine demand, experience has shown the following values to be very reliable for estimating chlorine demand:

  • Well Water - 1 to 2 PPM
  • Surface water - 4 to 5 PPM
  • Waste water - 8 to 10 PPM

Chlorine Gas Feeder Sizing
Process flow rate (GPM) X
Dosage (PPM) X 1440 minutes/day X 8.32 #/gallon
Chlorine Feed Rate (PPD)
1,000,000 PPM Concentration
This formula will calculate the PPD feed rate for chlorine gas based on the GPM flow rate and the PPM dosage.


Chlorine gas is supplied in steel cylinders, as a compressed gas in a liquid state. The pressure in the cylinder is dependent upon the temperature of the cylinder. Cylinder pressures will range from 28 PSI at 20° F to 191 PSI at 120° F. As a safety feature, the cylinders are fitted with fusible plugs that will melt at about 165° F. This is done to prevent the cylinder from exploding if it is in a fire situation.

For smaller water systems, chlorine gas is typically supplied in "150 pound cylinders," while larger systems will use "ton ( 2000 pound ) containers". The weight refers to the weight of chlorine that is being supplied, not the weight of the full cylinder. Full 150 pound cylinders will weigh from 235 ponds to 290 pounds. Full ton containers will weigh from 3,300 pounds to 3,650 pounds.

Chlorine gas is sold "by the pound". In addition to the price of the chlorine, a deposit will be charged for each cylinder. A typical deposit for a 150# cylinder is $200.00, while a typical ton container deposit is $1,500.00. The deposit on the 150# cylinder allows use for 180 days (six months), and the ton container deposit allows use for 30 - 90 days (depending on the supplier). If the cylinder is not returned within the designated time, a penalty will be assessed for each day over the allowed time.


To allow proper selection of a chlorinator injector, you need to know the specific "hydraulic conditions" at the site you want to chlorinate. This means that you need to know the pressure where the chlorine solution will be applied. Additionally, you will need to know the maximum capacity of the chlorinator, typically about twice the calculated feed rate.

If you are injecting the chlorine solution into a closed pipe, you need to know the pressure in the pipe. If you are injecting the chlorine solution into an open channel, or tank, you need to know how many feet of water will be above the point where the solution is injected.

With the above information, it is possible to select the proper nozzle for use in the injector. If the correct hydraulic information is not provided, the injector may not create enough vacuum to feed the gas into the water.

Most water well applications will use water from the well discharge to operate the chlorinator. In this application, you will need a booster pump to raise the pressure of the injector inlet water, so the injector will create a vacuum. Based on the information that you provide, Chemical Feeding Technologies, Inc. can recommend a correctly sized booster pump.

Chlorine Residual Testing:

Once you have your system installed and running, you need to take periodic chlorine residual tests to confirm that the pump is properly adjusting and also operating properly. A DPD chlorine residual test kit is the accepted test method for this procedure. Refer to Chlorine Residual Testing section.

Copyright March 1992, Chemical Feeding Technologies, Inc. Revised 04/19/99 Brochure 910

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