View report page

12
SANITARY CIRCUMSTANCES OF THE AREA.
Water.
The water is obtained from deep wells sunk into the chalk.
The wells are at New Barnet, East Barnet, Potters Bar,
Tyttenhanger, Roestock, Northaw, Hatfield and North Mimms.
It is pumped direct into the mains or into reservoirs at New
Barnet and Rowley Green. It is of great purity, pleasant to
drink, and free from organic matter or objectionable bacteria.
Like all London water, it is of considerable hardness varying
in the different wells from 22 to 26 degrees of hardness (1 degree
pf hardness is equal to 1 in 100,000 parts, 0.7 grains of carbonate
of lime in 1 gallon of water). Much of the hardness might be
remedied by boiling; this process precipitates the lime, but at
the same time by boiling out the oxygen renders the water less
pleasant to the taste. So far as is known, the hardness has no
deleterious effect, such as causing disease of the blood vessels or
the so-called rheumatic affections of joints. On the other hand,
those who use it are free from the diseases associated with the
consumption of softer water obtained from upland drainage
sources such as lead poisoning, etc.
The only possible source of contamination of water obtained
from the chalk would be through "swallow-holes," which are
cavernous openings commonly found at the junction of the
Reading beds and the chalk, into which streams disappear. One
of these "swallow-holes" is found near North Mimms, where
water from nearly 20 square miles of land disappears. The
whole of the water from North Mimms station is treated by the
most modern purification methods of sedimentation, filtration
and chlorination, and no contaminated water therefore can find
its way into the supply mains. The Water Company have an
up-to-date chemical and bacteriological laboratory in charge of a
fully qualified chemist; there is complete bacteriological control
and during the year 615 examinations have been made, 94.3
per cent. being B.coli free in 100 c.c.
Samples are sent periodically to independent analysts in
London for their examination, and the following report is characteristic
of such examinations:—