5
SIGNIFICANCE OF
POOL AND SPA TESTING
A major family leisure pursuit is the enjoyment of Swimming Pool and
Spa facilities world-wide. A basic necessity of Pool water treatment, to
ensure such enjoyment, is to maintain the water in a safe and pleasant
condition for the bathers.
In order to achieve such an objective, swimming pool water requires
testing on daily, and sometimes hourly bases for disinfection residuals
and pH. Equally important, Calcium Hardness and Alkalinity parameters
should be monitored on weekly bases to ensure the pool water is
maintained in a balanced condition, thus to avoid system failure because
of corrosion or scale formation.
DISINFECTION RESIDUAL AND pH CONTROL
In terms of swimming pool treatment, disinfection or sanitizing basically
means to rid the pool of bather pollution, destroy bacteria, and control
nuisance organisms like algae, which may occur in the pool, filtration
equipment, and piping.
There are a number of techniques used, namely, chlorine, bromine and
ozone dosing systems, of which chlorine is the most common.
Chlorine
Chlorine is a strong oxidizing agent that destroys mostly organic pollutants,
bacteria and can combine with nitrogen containing compounds, forming
chloramines. Only a part of the original quantity dosed chlorine, remains
active and continues its disinfecting action.
From the free chlorine you can distinguish combined chlorine, as that
part which combines with nitrogen containing compound and that is less
efficient as a disinfectant. The addition of these two parts gives total
chlorine. A pool manager needs to aim perfection where free equals
total chlorine, and thus to maintain the combined chlorine concentration
near zero. The presence of chloramines is not desired because of the
distinctive ‘swimming pool’ smell caused by combined chlorines like di-
chloramines. Beside this unpleasant odour it does irritate the eyes and
the mucous membranes.
Commercially chlorine for disinfection may be available as a gas (Cl
2
), a
liquid like sodium hypochlorite or bleach (NaOCl) or in a solid state like
calcium hypochlorite, chloro-hydantoins or chloro-cyanuric acid
compounds.
These compounds, once dissolved in water do establish equilibrium
