View report page

EXAMINATION OF WATER SUPPLIES
The Corporation of London exercise their functions with regard to water supply under the
Public Health Acts, 1936 and 1961, and the Water Acts of 1945, 1948 and 1955. There is also a
provision in the Offices, Shops and Railway Premises Act, 1963, which requires all employers of
shop and office workers to ensure that there is available to their staff an adequate supply of
wholesome drinking water.
In the City there are two sources of water supply:-
(1) From the statutory water undertaker, which in the case of the City is the Metropolitan
Water Board.
(2) From deep wells which supply water to private premises within the City. There are 108
such wells in use, a reduction of six as compared with the previous year, and they serve
52 premises.
The Metropolitan Water Board supply is usually safe, potable and wholesome at the point of
delivery to premises, but owing to storage conditions within the premises and other matters over
which the Board has no control the water can become contaminated. Observations, investigations
and sampling have been carried out by the Public Health Inspector responsible for this aspect of
environmental health in order to ensure that the water supply within all City premises is wholesome
and potable.

The water from the bore holes of the private wells comes from the London Basin, where it
collects in a hard grey chalk stratum which is protected from contamination by an impervious
stratum. The former stratum lies between 200 to 600 feet below ground-level. The water that it
yields is satisfactory in quality and quantity, contains some natural fluorine, and is non-plumbosolvent
with a total hardness of about 325 ppm. It is very unusual to find an adverse bacteriological
report on water abstracted from the well risers.
The sterilisation of this water is carried out by means of liquid chlorine, which is introduced
in the system so as to produce not less than 0.1 ppm. If this form of sterilisation is increased
there may be taste complaints. These usually occur at about 0.4ppm. Some supplies are, however,
sterilised by the ultra-violet light method.
The chalk stratum is rich in iron hydroxides which can sometimes be seen in the water as a
rusty discolouration. This can easily be eliminated by the use of diatomacious filters, which have
been fitted in some premises.
Swimming Baths
It is also the duty of the City Corporation to ascertain the purity of swimming bath water
within its area. There are three such pools in the City. These are visited weekly while the baths
are in use. Bacteriological samples are taken from the inlet and outlet. Combined residual and
free-chlorine are ascertained and the pH value is also taken. The total number of such samples
taken during the year was 475.
The following table shows details of bacteriological examinations of drinking water supplies
and swimming bath water.
10