Swimming Pool

In pre-historic times people swam, if they did, in natural waters. The Indus Valley (in modern
Pakistan) has the remains of a 60-metre mud brick pool lined with tar, built about 3,000BC.
Swimming pools were built by the ancient Greeks and Romans and used mainly for athletic and
military training. Roman emperors had private pools in which they also kept fish.
The first indoor pools in England were built early in the 19th century. Largely untreated, early
swimming pools got dirtier as the days went by and had to be emptied and refilled. When
charging came in, the price of a swim might fall as the water got dirtier. Another way round the
problem of pollution was to build pools that water flowed through on a continuous basis, usually
from a nearby stream. These days all but the humblest pool is quite a bit more complicated than that.

A typical swimming pool needs four major
• a tank (basin, shell)
• a circulation system – pumps, inlets and
outlets, pipework
• filtration
• a dosing system for treatment chemicals.
The basic idea is to pump water in a continual cycle, from the pool via filtration and chemical
treatment and back to the pool again. By this circulation, the water in the pool is kept relatively
free of dirt, debris and microorganisms (bacteria and viruses). Other processes are included –
heaters, for example. And it must be possible to make up water lost by evaporation, backwashing the filters and bathers carrying it out of the pool on costumes etc.