Apparently, an operator added hydrogen peroxide to the Rio Olympic Pool. The rationale behind the decision to add this chemical is not clear. It could have been intentional, as hydrogen peroxide is used in some swimming pools as an oxidiser. The problem is that the chemical is also used as a chlorine neutraliser. So when the hydrogen peroxide was added, it went to work and promptly neutralised all of the chlorine thus allowing organic plant life to thrive, since it now had water, sunlight, nu...
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It may be necessary to decrease the levels of chlorine on occasion and certainly following superchlorination. If you are going to be dumping a significant quality of swimming pool water for any reason, there would usually be a requirement to let the local water authority know and they would almost certainly require you to eliminate all traces of chlorine from the water before they granted permission to discharge (chlorine is harmful to aquatic organisms).

In normal operations, it would usual...

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pH stands for the 'power of hydrogen' and is a critical factor in the treatment of pool water. The recommended range for the pH level to be maintained at is 7.2 - 7.4. The reason that the pH level needs to be kept between these values is that the disinfection efficiency of the chlorine  falls off significantly at higher pH levels and the coagulant will also not be as effective. At lower pH values, the pool water will be too corrosive.

The effect of the pH level on the disinfection process is a...
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For the purposes of pool plant operation, chlorinated isocyanurates (also referred to as stabilised chlorine) can be thought of as a combination of cyanuric acid and chlorine. Why would a pool plant operator want cyanuric acid in addition to just chlorine? The answer is because in outdoor pools that are exposed to sunlight, the chlorine will get diminished by the UV in the sunlight. It needs an additional chemical to be added to prevent this from happening. This chemical is cyanuric acid. It ...
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Cyanuric acid is mostly used in outdoor pools. The reason for this is that chlorine is broken down by ultra violet light. Sunlight contains ultra violet light and when the sun shines onto an outdoor pool the chlorine gets depleted very quickly. The pool plant operator needs a way of 'stabilising' the chlorine and that's where cyanuric acid comes in. Cyanuric acid binds with the hypochlorous acid (the disinfectant in chlorine) and makes it more resistant to degradation by UV. The drawback is t...
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Balanced water testing is something that you should be doing weekly in order to determined whether you pool water is 'balanced'. This refers to whether the water is corrosive or scale-forming.

Corrosive water will eat away at grout, pump seals, pipework etc. (basically, anything it comes into contact with). Scale-forming water does the opposite of corrosive and instead of eating away at things it will form a scale on it (you're likely to see the effect of this on the heating element of your ke...
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Alkalinity is the amount of alkaline salts (carbonates, bicarbonates and hydroxide ions) present in the pool water. It is an important factor in the treatment of swimming pool water because it acts as a pH buffer. If your alkalinity levels are too low, you may find it difficult to control the pH level; when you add and acid, the pH level will drop too fast, then when you try to correct the problem, the pH level will shoot up past the level you want it at. If your alkalinity levels are too hig...
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Source water refers to where the mains water that supplies your swimming pool comes from. The water companies collect water from a variety of sources. Some of it is collected from ground waters such as wells and boreholes etc., and some of it is collected from surface waters such as lakes, rivers, streams etc. The ground waters have a higher content of calcium carbonate and are known as 'hard' water. The surface waters don't have such a high calcium carbonate content because they haven't perm...
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If your total alkalinity levels are too high, or too low; you will have problems controlling the pH levels. High total alkalinity causes 'pH lock', low total alkalinity causes 'pH bounce'. 

As pool plant operators, we all know that the pH of the swimming pool water is a critical factor. If the pH is too high, the disinfectant properties of the chlorine will be minimised. If the pH is too low, the swimming pool water will be too corrosive. Controlling the pH levels is usually a simple process w...
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If you carry out your weekly pool water balance test and find that the total alkalinity levels are low, you're going to need to add some sodium bicarbonate. This chemical will introduce some alkalinity into your pool without having too much of an effect on the pH level. The sodium bicarbonate that you add will go through various chemical reactions and some of it will convert into different chemicals according to what the pH level is at any given time. If the pH is high, some of the sodium bic...
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