Why does my pool smell?

Usually because of chloramines, not too much chlorine. The CDC explains that chlorine binding to the body waste swimmers bring in, things like sweat and urine, forms chloramines, which irritate skin, eyes and the nose. The fix is counterintuitive: shock the pool to burn them off, and have everyone rinse off before getting in, which the CDC says removes much of what forms them.

Most often algae getting started, or a water that has gone low on chlorine for a while. Test free chlorine, shock if it is low, and brush the walls. A fishy smell with a yellow film on shady walls is often mustard algae; see how to get rid of mustard algae.

Leaves and debris breaking down on the floor or in the baskets, with chlorine too low to keep up. Empty the skimmer and pump baskets, vacuum the floor, clean the filter and shock. If it comes back fast, the chlorine is not holding; check the stabilizer level.

Check the skimmer, the pump basket and the deep end for something dead. Frogs, toads and lizards end up in Florida pools constantly, and one rotting in a basket smells like sewage. Remove it, clean the basket and shock. See bugs and frogs in a pool.

Sulfur. Well water in parts of Florida carries hydrogen sulfide, and a pool topped up from that well can pick up the smell. Chlorine burns it off, so shock after topping up from the well. If the smell is around the equipment instead of the water, have the pool equipment checked.

Usually a dirty filter. Organic gunk caught in a filter that has not been cleaned in a while gives off a musty smell. Clean or backwash it; see how often to clean a pool filter.

Keep free chlorine steady, clean the baskets and filter, and get dead leaves and anything else rotting out of the water. A pool on steady weekly care with every chemical included, like our weekly pool service, rarely smells of anything.