A NUMBER of writers have re-joint after the main is in place. Heller ported the presence of coliform (3), in a field test run on a number of organisms in water samples obtained calking materials, discusses the advanfrom newly laid water mains, the tages of certain materials and observes source of the contamination clearly the difficulty of obtaining penetration. being packing materials in the joints.Calvert (1,2), to facilitate the evalu-Others have shown by laboratory stud-ation of calking materials, originated a ies that many packing materials sup-three-day cycle test in which the rate port the growth of coliform organisms of increase or decrease in bacterial and that large increases in numbers numbers indicates whether the matetake place within relatively short pe-rials might continue to contaminate riods of time. Packing materials, as water within the mains by supporting received, are sometimes contaminated growth of the bacteria within the joints. with bacteria as a result of the methods His procedure is essentially that used of preparation.. Such contamination by the authors, with the exception of serves as seed for future growth.several changes and refinements that Inasmuch as practically all soils, more easily make it possible for other particularly in inhabited areas, are cer-laboratories to duplicate the results and tain to contain coliform organisms, it is facilitate the establishment of a tentavirtually impossible, even when the tive standard procedure for testing joint packing is sterilized before being main-packing materials. The authors used in the field, to get it in place used standard dilution water instead of without contaminating it from the soil, tap water, as used by Calvert, because the walls of the pipe, or the laborers' tap water varies appreciably in different hands. Calvert (1, 2) discussed many parts of the country. It also seemed of these factors, including the difficulty advisable to start with materials and of sterilizing packing materials, and dilution water in a sterile condition, pointed out that to obtain disinfection inoculating these materials with a with chlorine, a chemical ordinarily used known quantity of a pure culture of in the water works field, it must be Esch. coli, and to follow with a similar applied in such high dosages that the test using Aer. aeroqenes, in order that packing material itself is frequently af-the packing material might be evalufected adversely. Every water works ated in terms of the organisms by man realizes how difficult it is for dis-which sanitary quality is usually infecting materials to penetrate the judged. 707 708
