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'The supply was derived from the following works and pumping
stations:—
River Thames (Southern Group).
'No new sources of supply were instituted and there were
no changes to the general scheme of supply in the area.
On account of hardness content and alkaline reaction the
Board's river and well water supplies are not considered to
be 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 to lead.
'Special tests for lead have been carried out during 1968 on
100 premises where a lead supply pipe is installed. The
premises were chosen to give an even distribution of samples
throughout the whole of the Board's area. Two samples
were collected from each premises; one was the first running
of water standing in the lead pipe overnight and the other was
a sample of water after running the tap for a few minutes.
'The results are set out in the accompanying table:—

'The above results are very satisfactory and the figures are
within the limits of the World Health Organisation European
Standards for Drinking Water Quality. This states that the
upper limit for lead in running water in the supply should not
be more than 0.1 mg/1 (Pb); but where water undertakings
continue to use lead piping the concentration of lead (as Pb)
should not exceed 0.3 mg/1 after 16 hours contact with the
pipes.'
Sampling of water supplies is an integral part of sampling duties,
and a growing responsibility is the bacteriological control of water in
swimming baths.
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