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Swimming Pool Water Treatment

Swimming Pool Water Treatment – it is fundamental requirement for the enjoyment of a clean and inviting swimming pool for owners to ensure that the water is free from harmful bacteria, viruses and algae.

Bacteria, viruses and other micro-organisms are carried into the pool by bathers and environmental pollutants; these can then multiply in untreated water.

In order to render these organisms harmless, a disinfectant must be used; these are products based on Chlorine and Bromine compounds and are here simply referred to Chlorine and Bromine.

However it is true to say that in general terms Bromine reacts in much the same manner as chlorine and consequently the text only refers to Chlorine.

For over a century, purification of pool water has traditionally been carried out by adding Chlorine.

Swimming Pool Water Treatment – Chlorine

Chlorine is an effective sanitiser when added to water in liquid, tablet or granular form and it offers a simple method of disinfecting pool water. In general, a level of two milligrams of Free Chlorine to one litre of water should be maintained at all times. Two milligrams per litre is a simple ratio and is equivalent to two millimetres in a kilometre. Its effectiveness is, however, dependent on the pH of the water.


pH is in simple terms an indication of whether the water has acid or alkaline properties. The pH scale runs from 1 to 14; 1 being 100% acid and 7 being neither acid nor alkali and 14 being 100% alkali. The higher the pH, the longer it takes the Chlorine to kill bacteria.

The pH value mus therefore be maintained within the range of 7.2-7.8 (ideally towards the lower end).


For outdoor domestic pools, Chlorine has long been the preferred choice. In liquid, granule or table form, it is safe and convenient to handle. Today’s user friendly multi-functional Chlorine santisers enable you to carry out several tasks simultaneously, killing harmful bacteria etc and keeping the water crystal clear.

A range of test kits are available to measure Chlorine and pH including simple kits containing tablets which change colour to indicate the concentration of Free Chlorine and the pH value of the water. Regular testing ensures that corrective action can be taken before an imbalance becomes a problem.

If the water in your pool turns cloudy or green the cause, in nearly every case, will be lack of Chlorine.   However if the water turns faintly turbid, it is because the pollutants in the water, mainly algae, are reproducing quicker than the Chlorine react.

In this case it is necessary to increase the Chlorine level sharply and in one go, keeping the circulation on continuously.

As always, it is a matter of preference, but your SPATA contractor will advise you of what is best for your pool to maintain it to SPATA Standards.


SPATA will always expect an approval pol company to reinforce safety messages and where applicable, to advise their clients to:

  1. Read and follow all instructions on the chemical manufacturers’ containers very carefully and to adhere to the instructions rigidly.
  2. Chemicals should NEVER be mixed together before adding them to the pool water (as fatal gas formation or explosions can occur). Always add a chemical to water and NEVER add water to chemicals.
  3. Never put one type of chemical into a container designed for another type, or use an empty container from another product.
  4. Always store containers in a cool, dry lockable area, separating different chemical containers.
  5. Ideally pre-dissolve the different chemicals individually in a separate designated bucket and pr fluid in around the perimeter of the pool, then wash the bucket in the pool after each application.
  6. Empty chemical containers should be washed out in the pool water, rinsed thoroughly and then disposed of in a normal household waste.
  7. Wash your hands after pool chemicals (the pool water will do!).
  8. Store chemicals away from children.
Know your capacity

Before adding chemicals to your pool it is vital to know its water capacity.

This simple formulae given below will enable you to calculate your pool’s approximate capacity in gallons or cubic metres (a cubic metre is equal to 1,000 litres or 220 Imperial gallons):



Dia (ft) x Dia (ft) x Average Depth (ft) x 4.9 = Gallons


Dia (m) x Dia (m) x Average Depth (m) x 0.8 – Cubic Metres



Long Dia (ft) x Short Dia (ft) Average Depth (ft) x 5 = Gallons


Long Dia (m) x Short Dia (m) Average Depth (m) x 0.9 = Cubic Metres

Rectangular or Square


Length (ft) x Width (ft) x Average Depth (ft) x 6.23 = Gallons


Length (m) x Width (m) x Average Depth (m) = Cubic Metres


Estimate dimensions equivalent to rectangular or circular and determine as above.

For further information please visit www.spata.co.uk