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Mar, 18, 1946 THE DISINFECTION OT NEW AND REPAIRED WATER LINES B efore any water system is put in to use a fte r is is rep a ired or when newly laid,, i t should be d is in fe c te d , flu sh ed and a b a c t e r io lo g ic a l examination of it s water content obtained. Unless f a c i l i t i e s w i l l be a v a ila b le f o r the in trodu ction o f e ith e r ch lo rin e or h e a v ily ch lo rin a ted water d ir e c t ly in to the mains on th e ir com­p le tio n , ch lo rin e d is in fe c ta n t s h a ll be placed at each jo in t o f the main p r io r to jo in tin g * The ta b le attached s ta te s the amount o f calcium h y p o ch lo rite (65$> a v a ila b le c h lo rin e ) to be added fo r each 20 f t * length of pipe to fu rn ish a r e s u ltin g solu tion o f 50 parts per m illio n and in s im ila r amounts p ro p o rtio n a l to th e ir percent o f a v a il­ab le ch lorin e* Inasmuch as a l l ch lo rin e d is in fe c ta n ts w i l l lo se stren gth on exposure to the atmosphere, i t is e s s e n tia l th at only fresh d is in fe c ta n t be used, th at p re fe ra b ly one o f the more s ta b le compounds be employed and th at the main be f i l l e d , allowed to stand, and then flushed not la t e r than one week a ft e r p la cin g o f the d isin fecta n t# A fte r the ch lo rin e con tain in g water has stood in the mains in contact w ith the pipe surfaces f o r the r e ­quired th ree hours, a ch lo rin e resid u a l at representa­t i v e poin ts should show at le a s t 0*5 parts per m illio n * D is in fe c tin g so lu tio n formed on f i l l i n g the lin e s h a ll be h eld in the main f o r at le a s t 3 hours and then flushed out so as to remove a l l chlorinous ta s te s which m i$it prove ob jection a b le* Mains s h a ll be flu sh ed u n til such time as the water flo w in g shows by the orth otolu din te s t a resid u a l ch lo rin e content not exceeding 0*3 parts per m illio n # Where c h lo rin e is added a ft e r com pletion of the main, i t s h a ll be introduced in to the lin e s in such a manner and in such quantity that a l l new mains w i l l r e c e iv e a ch lorin ated water con tainin g at le a s t 20 p arts per m illio n a v a ila b le chlorine# A ll mains, as discussed p re v io u sly , s h a ll be allow ed to stand f u l l w ith th is d is in fe c tin g so lu tio n at le a s t 3 hours and then flushed u n t il a ch lo rin e resid u a l content not ex­ceeding 0*3 parts per m illio n is indicated# W* W* White, D irecto r Div* o f Pu blic Health Eng,