In technical terms when you add pool shock to a swimming pool you are bringing the pool water to a chemical point known as breakpoint oxidation. At this point the bonds that hold together unwanted combined chlorine compounds called chloramines are broken down. At the same time the levels of freely available chlorine rise ensuring that your pool is being effectively sanitized. Chloramines are considered to be unwanted byproducts as they do not retain very much sanitizing strengths, are foul-smelling (causing a pungent ‘chlorine like’ smell) and can cause nose, eye and skin irritations.

There are a number of different shock treatments available on the market. It’s useful to break them down into two broad categories; chlorine-based treatments such as calcium hypochlorite, tricolor and dichlor and chlorine free shock that relies on a powerful oxidizer known as potassium monopersulphate, or MPH. The exact dosage that you’ll need to add to the pool will depend very much on the type of product you are using and the volume of water in your pool.  Here are some guidance notes to follow when adding pool shock:

• It’s a good idea to ensure that the pH levels of the pool fall between 7.2 and 7.6 before adding the shock treatment. pH levels have a strong influence on the effectiveness of chlorine and other sanitizing chemicals.
• Make sure all swimmers have exited the pool before you broadcast the treatment over the water and only allow them to return when the pool has re-balanced with chlorine readings falling below 3.0 ppm.  Non chlorine based shock treatments do not typically require as much pool downtime.
• If you are using a dry granular product this will need to be pre-dissolved in the bucket before being applied to the pool. It’s important when mixing chemicals in water to always ensure that you add chemicals to the water rather than the other way round.
• Run your pump and filter for at least 8 hours after applying the shock treatment to ensure the chemicals are well circulated through the pool.
• Pool experts recommend a weekly shock treatment for chlorine pools. But you may have to do this more often after periods of heavy rainfall, prolonged sunlight or if the pool is being heavily used.