Types of chlorine for swimming pools

In my conversations with pool owners, I often notice that most of them do not know what the pool cleaners they use to treat the pool water contain.

In the next few lines, I will explain what organic and inorganic chlorine are and what the difference is between them.

Inorganic chlorine

Inorganic chlorine products are sodium hypochlorite and calcium hypochlorite.

Sodium hypochlorite contains approximately 12.5% ​​chlorine, it is not recommended to store it for a long time and it breaks down very quickly in the pool water under the influence of light and heat.

It is mainly used in automatic dosing systems.

When using sodium hypochlorite, the PH value of the pool water increases.

Calcium hypochlorite contains a minimum of 65% chlorine. Calcium carbonate is also added to it. This product can only be used in pools with a water hardness below 14° d.H (German hardness).

If used in harder water, the PH value increases and there is a risk of limescale deposits on the pool walls.

Organic chlorine

Organic chlorine is available in two varieties:

• Fast-dissolving products (sodium dichloroisocyanurate)
• Slow-dissolving products (trichloroisocyanuric acid)

Both types are available in tablet or granule form.

The advantage is the high chlorine content of 60% - 90% and its durability. It can also be used in water with higher hardness. The disadvantage is the ingredient isocyanuric acid. It cannot dissolve in water and impairs the effect of chlorine.

The only way to reduce the amount of isocyanuric acid in the pool water is to add fresh water weekly. This process can be done, for example, when backwashing the sand filter.