Following on from our previous post regarding hand-dosing of chlorine, here is some guidance on superchlorination.

Superchlorination is not recommended as a routine or even occasional method of shock dosing to compensate for inadequacies in pool treatment. It is generally bad practice, and can generate unwelcome by-products. But if something has gone wrong – poor results from microbiological testing perhaps, or a catastrophic breakdown in treatment – it may be necessary to superchlorinate....

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Sometimes there will arise a need to introduce chemicals into the pool manually (hand-dosing). This is a potential hazardous activity and should not be performed by people who have not received the appropriate level of training.

General Procedures

• Always wear the appropriate PPE.

• Always add the chemical to the water, NEVER add water to the chemical.

• NEVER mix a chemical with another chemical. Only ever mix with water.

• Never hand-dose chemicals into the swimming pool when occupied.

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A few people struggle to fully understand the concept of what is known as 'breakpoint chlorination' during the pool plant operators course. In basic terms, as far as pool plant operators are concerned, breakpoint chlorination describes the point at which there is twice the amount of free chlorine than combined chlorine.

Imagine a swimming pool that has high levels of pollution. If you were to introduce some much-needed chlorine into the pool, it would quickly end up as combined chlorine as it ...
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Bromine is a disinfectant that works in a similar way to chlorine, in that it oxidises pollution on contact. The active disinfectant produced by the addition of chlorine-based disinfectants is hypochlorous acid, whereas the active disinfectant produced by the addition of bromine-based disinfectants is hypobromous acid.

Bromine-based disinfectants are not widely used in conventional commercial pools, largely because it is known to sometimes cause a condition known as ‘bromine itch’ in so...

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Ultra violet disinfection is a process whereby the swimming pool water flows through a UV chamber and is exposed to UV light. The UV light is harmful to bacteria and other micro-organisms because it mutates the DNA of the organism, which means that it can no longer reproduce. The UV chamber is installed in the plant room and once the swimming pool water has passed through the chamber, it will have been purified to the extent that any chlorine in the water will have also been removed. UV disin...
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Ozone is a disinfection method that uses ozone to oxidise contamination in the pool water. It is a more powerful oxidiser than chlorine and will actually oxidise (and therefore, remove) chlorine from the pool water when it passes through the ozone dosing system. It is a non-residual disinfectant, which means that no ozone remains in the pool water once it has passed through the ozone dosing system in the plant room. This is different to chlorine because under normal circumstances, there will ...
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Free chlorine is measured with the DPD1 test. It indicates how much of the total chlorine in the pool has not yet reacted with any pollution (ie, combined) and is therefore free and available to carry out it's purpose as a disinfectant.

There should always be enough free chlorine in the pool to minimise the risk of cross-contamination. The minimum recommended amount is 0.5mg/l. any less than this and you will need to shut the pool. The maximum recommended amount is 2.5mg/l. There is no need to...
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Oxidation is a process that has a disinfecting effect on swimming pool water pollution. It's basically a reaction between the oxidiser (the chlorine for example) and the pollution. The oxidiser will take electrons from the pollutant substances in the water, which breaks down and kills them. It's a very similar process to combustion (burning) and rusting. You can also observe the process if you peel an apple and see brown areas start to appear after a while (if you don't eat it, that is). What...
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