What is pool shocking? The technical term for shocking is “oxidation” — the process by which a molecule, atom or ion loses electrons. Chlorine has a naturally high electronegativity, which is why it binds well to the harmful molecules that build up in pools — preventing them from spreading. However, chlorine becomes ineffective as it gains electrons from binding to ammonia so the pool water must be periodically oxidized to maintain the chlorine’s effectiveness.

Why do pools need to be shocked? As a pool is used, the nitrogen contained in oils, sweat, and — yes — urine reacts with the chlorine in the water, forming chloramines. As the chlorine in a pool is converted into chloramines, it’s effectively “used up” and no longer available to kill germs. This is why “free available chlorine” or “FAC” is an important aspect of pool/spa water to measure. When the level reaches zero, it’s time to shock the pool to oxidize the organic material and refresh the free available chlorine.

To learn more about pool shock, we’ve created a guide: “Everything to Know About Pool Shocking.”