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The swimming pools are described as follows
1. 1st Class Swimming Pool (used for mixed bathing).
2o Men's 2nd Class Swimming Pool.
3. Ladies' 1st Class Swimming Pool.
4. Ladies' 2nd Class Swimming Pool.
The 1 surge mixed bathing pool has an area of approximately
4?500 sq0 ft. and the other three have each an area of
about 1,500 sq. ft.
All the pools are available for swimming in the summer
months (mid-April to mid-October), but during the winter months
only one of the smaller pools is open to the public for swimming.
The water used for swimming is taken from the Metropolitan
Water Board's supply at the commencement of the bathing season, and
throughout the season it is treated by a continuous filtration system.
Low pressure sand filters were installed in 1927 and a
continuous chlorination equipment added several years later. This
plant is now worn out and new equipment embodying the latest
improvements is being substituted. The work of replacing the
filtration plant for the large swimming pool and ladies' first
class pool was carried out during the winter of 1959/60 and
completed on 2nd May, i960.
The filtration process consists of drawing water from the
deep end of the cool through a suitable strainer and, after the
addition of coagulants to flocculate organic matter and to obtain
efficient filtration, the water is pumped to the top of four
Vertical Air-Scoured Pressure Filters. The water, before filtration,
is sterilized; this is done by introducing chlorinated water into
the circulating flow from "Wallace & Tiernan" Automatic Residual
Chlorine Control equipment, with hydraulic solution feeder for
automatic pH Control. This gives an accurate method of controlling
the dosage. The chlorinator automatically injects water
chlorinated to the correct strength and at the same time adjusts
the doses to suit varying bathing loads. The amount of chlorination
provided operates on the principle of "breakpoint chlorination"
and is recorded on a chart from which the degree of sterilization
of the water is known at any time during the swimming season.
The filter units consist of vertical closed cylinders
containing graded Non-Friable Leighton Buzzard Sand supported on a
bed of graded granite chippings, through which the water passes at
a rate of 230-gallons per square foot of filter area per hour. The
sand has to be washed regularly - this is done by steam and air
agitation and reversing the flow of water, which runs to waste and
carries impurities with it. Water taken from the pools is used
for the washing process.
The filtered water is then aerated, thereby assisting in
the maintenance of bacterial purity. It is then heated by
calorifiers to about 75°F« It re-enters the swimming pools
through suitable inlets at the shallow ends. Scum troughs are
being provided on the sides of the pools which draw off any
pollution which may accumulate near the surface, together with any
dust which settles thereon.
The new equipment has been designed to give a turnover
period up to 5^" hours, which is about twice that obtained from the
old plant. By this means, quicker purification of water is
obtained and is particularly beneficial during peak periods.