TOWNS.

TABLE I-Concluded

Summary of Water Supply Examinations by Towns, July 1, 1924,

*Not inclusive of 21 samples representing sources used for bathing. † Not inclusive of sources used for bathing.

Analyses of Public Water Supplies

In Table II, is presented the results of examination of public water supplies for the presence and relative numbers of B. coli, the organism typifying fecal contamination. Because of lack of space, results indicating chemical and physical data are not here given.

In comparing these results for the various towns and cities, as shown in the table, it is important to avoid giving undue weight to unfavorable findings where such may involve but a half dozen samples or less during the period. Also, in considering the significance of positive findings it needs to be borne in mind that in a section of this character, remote from the large centers of population, the presence of these fecal organisms is to a very large extent to be asscribed to cattle and to some extent to wild animals and that therefore as an index of pollution far less seriousness attaches than would be the case were domestic sewage responsible. But, even so, we are justified in exacting, as evidence of a satisfactory degree of purity and cleanliness, compliance with the standards of the United States Public Health Service, which demands the absence of B. coli in one cubic centimeter portions, with no more than twenty percent of positives in a series of ten cubic centimeter portions examined.

Number, Source and Ownership of Public Water Supplies

An analysis of Table II discloses the following facts concerning the number of systems, ownership and sources of supply.

In connection with any comparisons with other states based upon the proportion of public water supplies subjected to purification treatment, it needs to be understood that the total here given is inclusive of quite a number of small and relatively unimportant systems, also that watersheds with no population, or but sparsely populated, are the rule.

Cross Connections

Money and effort expended in insuring pure water are largely wasted if the supply in question is to be exposed to the hazard of pollution through connections with it of polluted sources used for industrial purposes. A majority of manufacturing plants make use of the dual protection represented by supplementing the municipal supply through resort, by means of a fire pump, to a nearby stream or small pond, usually polluted, the separation between the two systems being dependent upon check valves.

In the past it has been found that the common practice was to depend upon a single cast iron check, usually buried in the ground, never tested, and in fact, all but forgotten by the mill superintendent, while its very existence may have been unknown to the water supply officials. Under the law enacted in 1917 the latter are held responsible for the installation and proper inspection of such protective devices as may be approved by the state board of health, or the latter may require the complete severance of the two systems wherever, in its judgment, the situation calls for this.

In a few states, as well as in many cities at the present time, no connection whatever of a polluted secondary supply with a public system is permitted, a somewhat drastic step which has scarcely seemed called for by the average situation in New Hampshire provided an effective protective device is interposed between the two systems, and is periodically inspected. Since the enactment of the law referred to attention has been given to this matter by this department as time has permitted, and during the past year, especially, considerable progress has been made.

TABLE II

Results of Examination of Public Water Supplies for B. Coli

(1).

(2).

(3).

Following is a list of the abbreviations with references used in this table:
Ownership; M, town or precinct; P, private.

W, Well or wells; S, spring or springs; Str, stream; L, lake or natural pond;
StrR, large impounding reservoir on stream; SStr, springs and stream; Wstr,
wells and stream.

Cl, chlorination; SSF, slow sand filtration; MF, mechanical filtration; A, aeration. (4). In the case of treated supplies, includes faucet samples only.

(5).

Figures should not be used as a basis of comparison where the indicated number of samples examined is very small.