If you’re one of those brave souls who owns a backyard pool, you already know the struggle. You test the water on a Saturday, it’s perfect, and by Sunday evening, it’s a ghost town of chlorine. That’s because chlorine evaporates fastest in the top few inches of water.
How Long Does It Take Chlorine to Evaporate From Water?
Think of it like steam rising from a hot cup of tea—except the steam is invisible and keeps your pool from turning green. In direct sun, you can lose up to 90% of your chlorine in just two hours. That’s why pool experts scream about using a cover.
My neighbor, Dave, once left his pool uncovered for a week in July. He came back to what he described as “a swamp with a diving board.” A little dramatic, Dave, but he wasn’t wrong. Lesson learned: cover it, or buy more chemicals.
A Word on That “Pool Smell”
You know that distinct chlorine smell everyone associates with a clean pool? Well, brace yourself—it’s not actually chlorine. That smell is chloramines, a byproduct formed when chlorine reacts with sweat, pee, and dead skin cells. Gross, I know.
When you smell that strong odor, it means the chlorine is working hard—and already starting to evaporate as a gas. So if you walk into an indoor pool and your eyes burn, it’s not too much chlorine. It’s too little active chlorine and too much human baggage.
The takeaway? A pool that smells like a chemistry lab needs more chlorine, not less. But also, please use the bathroom before you jump in. For everyone’s sake.
