Bob Lowry on Dialing in Free Chlorine the Right Way
Pools that “won’t hold chlorine” are one of the most common and expensive headaches in pool maintenance, especially for pool service pros trying to stabilize water fast. When someone says they’re adding two or three gallons of liquid chlorine a day to an 8,000 to 10,000 gallon pool and still reading near zero free chlorine, the first move is not panic dosing. It’s investigation. Chlorine demand usually has a cause: organics, contaminants, or active growth. Start by looking beyond the water test and into the yard, the deck, and the daily habits around the pool. Grass clippings, fertilizer drift, landscaping debris, and rain runoff dripping from dense vegetation all add organic load that chlorine must oxidize. Even well-meaning actions like washing the deck so dirty rinse water flows into the pool can wipe out chlorine overnight. Once you suspect contamination, think like a detective and list every source of oxidizer demand. Heavy bather load can create big swings, especially ...