Swimming pool owners have one very important job when it comes to their pools, and that's to always ensure proper sanitation of the water. The common method of making sure a swimming pool remains sanitary is through chemical disinfection, usually with chlorine. Also, swimming pools need to be superchlorinated, or shocked, on a regular basis, usually by using higher levels of chlorine than normal. Chlorine is chlorine, fortunately, and even laundry bleach in the right amounts can be used to shock a pool.
Common household laundry bleach contains sodium hypochlorite, the liquid form of chlorine. Most laundry bleaches range from 5.25 per cent to 6 per cent sodium hypochlorite by volume. Liquid pool-specific chlorine also contains sodium hypchlorite, though it's at a higher strength of up to 14 per cent by volume. Therefore, if enough laundry bleach is added to a swimming pool, it can raise chlorine levels high enough to effectively shock, or superchlorinate, the pool.
When you shock your pool, you greatly elevate its chlorine levels. Effectively shocking a pool requires chlorine levels from 10 to 25 parts per million (ppm), depending on why the pool's being shocked. It takes about 1 gallon of bleach per 30,000 gallons of water to raise pool chlorine by 2 ppm. To achieve a 10 ppm swimming pool chlorine level using bleach, you'll need to add up to 5 gallons of bleach.
Bleach is very alkaline, with a pH that runs from 10 to 16. A swimming pool's minimum pH should be 7.2 to 7.8, though 7.4 to 7.6 is best. Adding bleach to a pool to shock it will raise pool pH above 8. It's best to shock a pool at dusk and measure chlorine and pH the following morning, lowering pH if necessary. It takes 3 quarts of muriatic acid per 30,000 gallons in a pool to lower pH below 7.8.
When using bleach to shock a swimming pool, use only unscented or "original scent" bleach brands. Never use splashless or scented bleaches in a swimming pool because they contain other chemicals that can interfere with a pool's water chemistry. Bleach is also sensitive to intense light and will degrade quickly in a swimming pool if you shock your pool in the bright sunlight. Lastly, when shocking a pool with bleach, avoid splashing any on your skin or into your eyes.
Swimming pool chlorine and pH chemistry balances are dependent on each in order to work effectively. When adding bleach or any other form of chlorine to a pool, always measure pH once finished. If pH in a swimming pool is too high, chlorine will work very poorly. If a pool's pH is too low (below 7), the chlorine in the pool will begin to rapidly disappear, leaving the pool vulnerable to contamination. The pH can be raised by adding soda ash in recommended amounts.