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m Eas Rate of Application Water from the source of supply shall be_controll ed to flow verv slowly into the newly laid: pipe line during the application" of chlorine. The rate of chlorine gas-water mix­ture flow shall he in such proportion to the rate of water entering the pipe that the chlorine dose, applied to the water entering the newly laid pipe shall be at least 40 to 50 parts per million. Back Pressure Prevented Back pressure, causing a reversal of flow in the pipe being treated, shall be prevented. Retention Period Treated water shall be retained in the pipe long enough to destroy all non-spore-forming bacteria. This period shall be at least three hours and preferably longer as may be directed. After the chlorine residual has been retained for the required time, the chlorine residual at pipe extremities and at other representative points shall be at least 5 parts per million. Chlorinating Valves and Hydrants In the process of chlorinating newly laid water pipe, all valves or other appurtenances shall be operated while the pipe line is filled with the chlorinating agent. Final Flushing and Test Following chlorination, all treated water shall be thoroughly flushed from the newly laid pipe line at its extremities until tire replacement water throughout its length shall, upon test, both chemically and bacteriologically, be proven equal to the "water duality served the public from the existing water supply system, and approved by the Public Health Authority having jurisdiction. Repetition of Procedure Should the initial treatment, in the opinion of the Engineer, prove ineffective, the chlorination procedure shall be repeated until confirmed tests show that water sampled from the newly laid pipe conforms to the requirements. April 17, 1948 11