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General formulation to calculate  how much bleach is needed to add to a tank or a pipeline to disinfect it to a given chlorine residual using a given disinfectant. Usually someone wants to know how to meet an AWWA Standard (like C651-92, Disinfection of Water Mains). The equation below should be used to estimate the amount of sodium / Calcium hypochlorite (Chlorine Water is 6.00% sodium hypochlorite) needed to disinfect a given quantity of water to a desired chlorine concentration. </p>
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                                                                        req'd residual in ppm<br />
  Valume of hypo  =  volume of water  x  (  ----------------------------- )<br />
                                                                           1,000,000 x hypo %</p>
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<span face="">For example , say you had installed a new 5,000 gallon tank and wanted to make sure that you had at least a 100 ppm solution of chlorine in it.</span></p>
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<span face="">How much 6.00% Hypochlorite would you need to add  ?</span></p>
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<span face="">(5,000 gal x 100 ppm) / (1,000,000 x .06) = 8.33 gallons</span></li>
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<span face="">How much 12% Hypochlorite solution would you need ?</span></p>
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<span face="">(5,000 gal x 100 ppm) / (1,000,000 x .12) = 4.17 gallons </span></li>
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<span face="">If you use calcium hypochlorite (the white, powder version of chlorine, like HTH pool cleaner), the equation becomes:</span></p>
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<span face="">                                                                                                              req'd residual in PPM<br />
Wgt. of Calcium Hypo (lbs)= gal of water x 8.33 lb / gal m x   ( ----------------------------- )<br />
                                                                                                               1,000,000 x hypo %</span></p>
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This is simply the previous equation multiplied by the conversion factor of 8.33 pounds per gallon of water.</li>
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Let's assume that we still need to disinfect 5,000 gallons at 100 ppm.</p>
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How many pounds of 65% calcium hypochlorite (HTH pool cleaner) are needed?</p>
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(8.33 lbs/ gal. x 5,000 gal x 100 ppm) / (1,000,000 x .65) = 6.4 pounds</li>
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