An outdoor swimming pool is a deposito or reservoir of water; unlike a normal reservoir the water is not consumed.

Add to this water human beings, human waste, cosmetics, sun creams, garden debris, farmers pesticides – all of which combine as “phosphates” which is food for algae, viruses, bacteria all the root cause of infection, illness and ugly water.

To make matters worse pools are in sunny areas and aggravated further by heating the water which rapidly increases bacteria and virus multiplication.

To survive this onslaught requires the use of technology, the application of science, constant research and the collection of multiple data. To understand the effect, we need to find ways of dealing with the cause.


  • Understand the objective – To remove harmful bacteria viruses, prevent infection & illness.
  • The water needs to look clear and beautiful – dissolve solids & kill algae.
  • Research & understand the work of the scientists.
  • Research & understand the best technology to achieve the needs of the scientists.
  • Understand the relationship between chemicals and pool plant – building materials and most importantly human beings.
  • Consider Economy and practicality of ownership.

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The key effects of poor pool hygiene?

  • Red eye syndrome.
  • Irritated or itchy skin
  • Breathing difficulties – aggravated asthma
  • Bleached clothing
  • Foul smelling swim wear
  • Green hair
  • Ugly green water and algae slime
  • Over stabilisation

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How to make a Swimming Pool Hygienic?

Water Chemistry – The chemicals:

Swimming pool water chemistry is no mystery. It is a fine balance of water hardness, carbonates, acids and disinfectant. Considering the ability of water to dissolve solids, remove infection and illness and the interaction of the different chemicals used.

Then finally to understand how all of this affects us humans. After all we do not want to enter a toxic chemical bath.


Outdoor pools are best treated with Chlorine. This is a very effective sanitiser of most bacteria, viruses and will control algae.
Chlorine is bleach, too much is harmful to humans. Chlorine will be rapidly absorbed by the sun unless protected. An acid, developed in the 1950’s (Cyanuric acid – CYA) helps protect chlorine from the sun. But it reduces chlorine efficiency. CYA needs to be balanced.
Over stabilisation is the term that describes too much CYA which renders chlorine unable to oxidise, and goes on to cause lots of damage to pool plant, flexible pipes, pool surfaces, allows build up of chloramines which causes red eye, irritable skin, asthma and allows infection to spread throughout the pool.
(follow link to technical articles…” chlorine”)

Saturation Index:

This is the term that describes the waters ability to dissolve solids, and is ultimately the measure of the waters hardness and alkalinity. When balanced correctly it prevents PH “bounce”, and enables chlorine to work effectively. When out of balance PH will swing, chlorine becomes ineffective. When too acidic it damages pool surfaces, when too alkaline the water becomes cloudy.

Testing and chemical dispensing:

Reckless addition of chemicals by guess work, without full testing and knowledge is like asking a greedy landlord to treat an alcoholic with brandy.

Notes are taken and recorded. These records allow a careful and considered protocol to be adopted.
All chemicals perform best when dispensed in small controlled quantities.
Chlorine controlled at 4ppm (7.5% of 50ppm CYA) in the summer will need daily dispensing, when daily consumption is 2ppm or more (depending on use, heat and location).
CYA takes as long as 2 weeks to fully dissolve. It can only be removed by draining, it does not go by evaporation.
Saturation index chemicals needs to be adjusted one at a time. First the hardness needs to be correct then PH. Never add acid & hardness together, as one counter acts the other.
Avoid over stabilisation – always know the CYA level – never use Chlorine tablets, they contain CYA, dissolve slowly and add to the build up of toxic waste chlorine, cause red eye, irritable skin, asthma etc.