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115
pipes are flushed out and refilled; samples of water are
then collected from these treated mains; and the mains
are returned to service only after the analytical results
are found to be satisfactory.
The quality control from these laboratories is carried
out by means of daily sampling from sources of supply,
from the treatment works or well stations, from the
distribution system, and through to the consumer. Any
sign of contamination or any other abnormality is
immediately investigated.
(c) (i) The Board has no record of the number of structurally
separate dwellings supplied in your area, but
the population supplied direct according to the Registrar-General's
estimates at 30th June, 1971, was
304,178.
(ii) No houses were permanently supplied by standpipe.
(d) No artificial fluoride is being added, and where the
fluoride content is indicated in the analyses it represents
the naturally occurring fluoride in the water.
2. (a) The supply was derived from the following works and
pumping stations: —
River Thames—derived water from The Thames
Valley Group. Well water from Eynsford, Horton
Kirby, Lullingstone, North Orpington, Orpington,
Shortlands, Sundridge and West Wickham Pumping
Stations.
No new sources of supply were instituted and there
were no changes to the general scheme of supply in
your area.
The number of samples collected and the bacteriological
and chemical analyses of the supply from the
above sources after treatment are shown on the
attached sheets.
(b) On account of their hardness content and alkaline
reaction the Board's river and well water supplies are
shown to be not plumbo-solvent. It should, however,
be appreciated that all types of water pick up varying
amounts of metal from the material of water piping
particularly when it is newly installed; this applies to
copper, zinc, iron and also lead.