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Earth current meter data, obtained and interpreted by an experienced engineer, give quantitative information on the current in the earth at a particular point, and to this extent generally afford an accurate estimate of electrolysis conditions in the small area immediately adjacent to the test electrode.

CHAPTER XIX

WATER CONSUMPTION

Water consumption in American cities is large in practically every instance and frequently it averages more than 100 gallons per capita daily. Instances of average water consumption of 75 gallons are comparatively rare, notwithstanding that this figure is about three times the record shown by representative European cities.

Recently obtained statistical data from some of the larger American cities are set forth in table 22.

Appreciation of why American communities require so much more water than those in Europe involves an inquiry into a comparison of domestic consumption, industrial consumption and the control of waste. To these questions is related that of metering.

Domestic consumption

Various estimates have been made as to the volume of water actually used and necessary for domestic consumption. A few years ago such figures ranged from 25 to 30 gallons per capita daily. More recently these figures have been increased by about 5 gallons. It depends upon the type of community, its climate and needs for the use of water outside the house for sprinkling lawns, cleaning automobiles and irrigation of gardens.

A pitometer survey at Toledo of three classes of districts was checked by gagings in sewers built in practically impervious clay through which there was substantially no leakage either from or into the sewers. These observations were made during the first week in March when no water was used for lawn irrigation purposes. For the highest type of residential district the water consumption was 48 gallons per capita daily. For two lower classes the consumption was 32 and 15 gallons respectively. The weighted average for three classes of districts was 34 gallons per capita daily.

In considering such data as above set forth it is to be borne in mind that there are 5 to 10 gallons per capita daily of water used for public purposes in carefully managed communities. These include water for fire protection, sewer flushing, public buildings

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and the like. But after the figures above noted are applied to the entire population there is still to be taken into account the gross waste of water sometimes found in flushing sewers or washing streets or various other forms of waste which are dealt with later as a separate heading.

Neither do these figures, amounting to perhaps 40 gallons per person per day for domestic consumption, deal with two substantial, and in most cities, legitimate items of water consumption, namely, (a) unavoidable leakage or unaccounted for water; (b) use of water in large industries.

Under the item of unaccounted for water in cities where all services are metered, it is seldom possible to account for more than 70 to 80 per cent of the water delivered into the distribution system. On an average it is found that the summation of all individual meter readings do not equal for a given period more than 75 per cent of the reading of the master meter through which all of the water is delivered into the distribution system.

Consumption of water by manufacturers and large industries

In some cities practically all water for industrial use is obtained by the consumers themselves. This situation is almost completely

true in Memphis, where the city consumption averages 70 gallons per capita daily and where investigations in 1921 indicated that practically as much more water was used by various industrial concerns, hotels, stores and other large users who could get water from wells of their own from the same sub-surface strata as that from which the city supply is drawn.

In eastern Massachusetts and elsewhere there are fairly large cities in which large industries draw most of their water supply from power canals or wells so that their use of city water is limited almost to water for drinking purposes.

There are other cities where more than one half of the total water consumption is consumed by industrial and commercial establishments..

Illustrative of the varied influence of this factor, reference is made to the following table.

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Generally speaking, large cities use more water per capita than small cities. As a rule this is due to the influence of industries. Naturally there are exceptions to this rule, although waterworks men generally estimate that a city, as it continues to grow, will use more water per capita in the future than it has in the past, assuming that there will be equal control of water waste.

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