How to Properly Shock Treat a Swimming Pool

Proper maintenance keeps swimming pool water clear.

"Shocking" a swimming pool or spa is a necessary maintenance task that keeps the pool water safe and free from irritants. Organic compounds in the water can irritate swimmers as well as prevent the pool's chlorine content from properly sanitizing the pool. Periodically shock treating the pool will eliminate these organic compounds, allowing proper long-term maintenance of the water chemistry.

Things You'll Need

• Water chemistry testing kit
• Pool chlorine

Instructions

1. Take a sample of the swimming pool water according to the directions in the water chemistry test kit. The test may require that you use a specific amount of water for accurate readings.

2. Perform a DPD test on a water sample using a DPD No. 1 tablet. Record the reading to determine the water's free chlorine level. Add a DPD No. 3 tablet to the same water sample, then record the result as the water's total chlorine level.

3. Calculate the combined chlorine level as the difference between these two figures. If both readings are the same, then there is no combined chlorine level. If the total chlorine level exceeds the free chlorine level, this is your combined chlorine level.

4. Calculate the amount of free chlorine needed to "shock" the pool's system back into proper water chemistry. For every 1 ppm worth of combined chlorine, you must add 10 ppm of chlorine to remove it. This breakpoint chlorination will destroy organic waste in a process known as oxidation.

5. Add chlorine to the swimming pool according to your calculation. Speak to a swimming pool specialist for help determining the proper ratio of chlorine to swimming pool water to make sure that you achieve superchlorination.

Tips & Warnings

• Superchlorination, which is the act of overchlorinating the pool or "shocking" the pool, is essential in removing organic compounds such as combined chlorines or chloramines. If you do not add enough chlorine, you may exacerbate the problem rather than remedy it.

References

• "Pools & Spas"; David Short, et al.; 2008
• "What Color Is Your Swimming Pool?"; Alan E. Sanderfoot; 2003