Chemicals to Use When Opening a Swimming Pool


As Pool and Spa notes, adding chemicals to the water is the last step in opening your swimming pool for the season. While some of these chemicals help sanitize the water by killing microorganisms, others help balance the water's chemistry by adjusting pH and alkalinity levels. If you plan to open your pool soon, take into account the various chemicals you likely will need.

Chemicals for Shock

  • Shock is a powerful and usually highly-chlorinated chemical that you should add to your pool at the beginning of the swimming season. According to Pool and Spa, adding shock---or shocking the pool---will kill off the algae and bacteria that accumulate over the months when the pool is not in use and the water is stagnant. For particularly dirty and green-colored pool water, you may need to add 3 or 4 gallons of the chemical on the first day and, if the water does not clear up, another 3 or 4 gallons on the second day.. As Learn About Pools notes, the most common type of shock uses calcium hypochlorite as its active ingredient in concentrations of 65 or 75 percent. Other varieties include lithium shock, which uses lithium hypochlorite as its active ingredient, and chlorine-free shock, which relies on potassium monopersulfate.

Chemicals for pH

  • According to Pool Manual, on the pH scale, wherein 7.0 is neutral, 14.0 is perfectly alkaline, and 1.0 is perfectly acidic, your pool water should have a range of between 7.2 and 7.8. To accomplish this, you need to test your pool's pH, and add in either pH increaser, if your pH is too low, or pH decreaser, if your pH is too high. Two main types of pH increaser are used: sodium carbonate and soda ash, the latter of which is an anhydrous, or dehydrated, variation of the former. PH decreasers also come in two forms: muriatic acid, also known as hydrochloric acid; and sodium bisulfate.

Chemicals for Alkalinity

  • In addition to testing your pool for general pH levels and adding pH increaser or decreaser as needed, you must perform a test specifically for alkalinity. As Pool Manual notes, while pH tests determine whether water is acidic or alkaline, alkalinity tests show how much alkaline material is in the water. To eliminate excess alkalinity, use a pH decreaser like sodium bisulfate or muriatic acid. However, to increase alkalinity, you need an alkalinity increaser, which consists of sodium bicarbonate. According to Pool Manual, some pool cleaning experts recommend using less expensive, cooking-grade baking soda for increasing alkalinity as opposed to a specialized product. However, while baking soda is sodium bicarbonate, manufacturers do not intend that it is used in pools and offer no instructions on how to use it in such an application.

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