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the Eltham zone is supplied from Wilmington, Darenth and Bexley
wells with an additional small proportion from the low zone should
the occasion arise; the Bromley zone to the south of the borough is
supplied from Shortlands well and on occasions with additional Thamesderived
filtered water.
All the Thames-derived filtered water is chlorinated after filtration.
In the case of Hampton, a contact tank has been built where the chlorine
has time to exert its full effect before the water is pumped into supply;
consequently the water in the distribution system is free or almost free
from residual chlorine. All the well water is chlorinated and, in
addition, contact tanks are provided at Deptford, Wilmington and
Bexley Wells; any residual chlorine is wholly or almost completely
removed before the water leaves the works.
Bacteriological analyses are made five times a week of all supplies
and consistently satisfactory results have been obtained. Chemical
analyses are also made at regular intervals. In the case of the riverderived
supply the water is tested bacteriologically and chemically at
all stages of purification. All new and repaired mains are chlorinated
before being restored to use and samples of water from them are tested
bacteriologically.
None of the supplies is plumbo-solvent.
The closest watch is kept for any form of contamination and
immediate action is taken if the results of the analyses are not up to
standard.
Appended are the average results of the chemical and bacteriological
analyses of the various supplies as forwarded by the Metropolitan
Water Board:—