Chlorine Metering Pump Sizing
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Household Bleach is 5 1/4% Sodium Hypochlorite
Liquid Pool Chlorine is 12 1/2% Sodium Hypochlorite
In computing your metering pumps settings and solution strength, keep in mind that its best to make up fresh solution once a month. The chlorine solution loses strength as it ages, and is sensitive to heat and light. Generally, keep solution tank out of the sun and use fresh solution at least once a month for best results.
How To Figure out What Size Pump to Use, and How To Set the Speed and the Stroke To Achieve Proper Dosage:
Step One: Determine Flow Rate of the water stream you are injecting into, in Gallons Per Minute (GPM) or Liters Per Minute (LPM).
Step Two: Determine the parts per million of chlorine you are trying to achieve (PPM).
Step Three: Use the formula below to compute the gallons per day and select the pump.
Step Four: Adjust the output of the meterng pump to achieve proper dosage.
Multiply the Flow Rate (in gallons per minute) times the Applied Dosage in Parts Per Million Desired times 1440. Then divide by the Solution Strength being used.
Household bleach is approximately 5% chlorine, pool chlorine is 10 to 12%.
Regarding the solution strength: If you dilute household bleach (which is 5% chlorine) by using 9 gallons of pure water to 1 gallon of household bleach, you end up with a solution strength of approximately 0.5% or 5000 ppm. In other words, household bleach has a solution strength of 50,000 ppm, and if you dilute it with 9 gallons of water, you end up with a solution strength of 5,000 ppm. When using the calculator above, you would enter 0.5 since it calculates in terms of percentages. 0.5% is the same as 5000 parts per million.
Regarding setting the output of the metering pump: You can vary the applied dosage of chlorine by adjusting the solution strength and by adjusting the output knob of the metering pump. After you use the formula below to compute the gallons per day adjust the pump to end up with the desired applied dosage.
Example: Assume that you have a well pump that has a flow rate of 12 gallons per minute (12 GPM) and that you want to inject 2.0 ppm of chlorine into the water. You have decided to use a solution strength of 5,000 ppm. There are 1440 minutes in one day and the formula will tell you how many gallons of chlorine you will use for every 24 hours the well pump runs. This is useful because the metering pumps are rated in output per 24 hours.
The formula is: 12 GPM x 2.0 PPM x 1440 and then divided by 5,000 = 6.9 Gallons Per Day
This means that you need a metering pump that has an output of 6.91 gallons per day. You can use the Stenner 45MHP10, which has a maximum output of 10 gallons per day, and set the pump to 69% level, since 6.9 is 69% of 10.. This way the pump will pump at a rate of 6.9 gallons, for every 24 hours the well pumps runs. Theoretically this will give you an applied chlorine dose of 2.0 ppm.
Your well pump might run for 1 hour a day, so at this rate you would use 6.9 gallons of your solution every 24 days. It is better to add more solution every one to two months as the solution can lose its potency over time.
Whatever your initial setting be sure to test for total and free-chlorine and then adjust the pump and/or the solution strength to achieve your desired free-chlorine residual in your piping. For instance a common free-chlorine residual desired is between 0.2 and 0.6 ppm. You injected 2.0 ppm and after combining with odors in the water, or disinfecting the water of bacteria, you find you have no free-chlorine residual. Then you would want to turn up your metering pump output, or adjust the solution strength.
See more information on the Stenner 45MHP10
See more information on the Free and Total Chlorine Test Kit
Find out how to determine your wells flow rate in gallons per minute:
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