At times, swimming pools need a little shock treatment. The basic purpose of pool shock is to restore the proper amount of free chlorine in the pool. You shock your pool by adding a powerful chlorine compound to the water. If done properly and regularly (most experts recommend once a week), this keeps the pool clean and healthy for swimmers.

Proper shocking keeps a pool healthy and clear.

Chlorine and Pools

The use of a swimming pool adds bacteria, algae, and other undesirable organic substances to the water. The heavier the use, the dirtier the water gets -- a problem compounded by heat, sunlight and rainfall. While your filter system helps to rid the water of dirt, leaves and large particles, an inadequate level of free chlorine in the pool can still present a problem.

Freeing Up Chlorine

When chlorine is added to pool water, it combines with ammonia and nitrogen compounds, which helps it to kill bacteria and organic matter. This cleans the water, but it also lowers the amount of free chlorine available. The dirtier the water, the more chlorine is combined and the less free chlorine is present.

You measure how effective chlorine is by comparing the levels of total chlorine and free chlorine with a test kit. These amounts should nearly match. If they don't, the free chlorine is not at a sufficient concentration to clean the pool. Shocking a pool restores the needed amount of free chlorine to the pool water.

Fighting Bacteria

A proper free-chlorine level allows the chemical to efficiently rid the pool water of bacteria and microorganisms. This is especially important after a period of heavy pool use, when the bacteria level is high, and the pool water contains large amounts of sweat and other bodily fluids. Pool shock also helps rid the pool of any algae forming in the water, and fights mold and mildew from forming on tiles, drains and other surfaces.

Clearing the Water

A pool shock can rid the pool of a heavy "chlorine smell" (which actually arises from the presence of other compounds), and to clear the water for a fresh, clean appearance. If a pool shock results in cloudy water, that means the algae and bacterial levels were already high, and the shock treatment created a high concentration of dead microorganisms. You can solve this problem with a specially prepared pool-clarifying compound.