Pool chemical balancing

The five numbers we care about

Chlorine gets all the attention, but it only works when the rest of the water lets it. pH controls how active the chlorine is. Alkalinity keeps pH from swinging. Stabilizer, which is cyanuric acid, shields chlorine from the sun, and in Florida that matters more than anywhere. Calcium hardness decides whether the water leaves your plaster alone or starts pulling from it.

When one of those is off, the others drift. High stabilizer is the most common problem we find on pools that have been dosed with tablets for years. The water looks fine, the test strip says chlorine is present, and yet algae keeps coming back because the chlorine is locked up. The fix is a partial drain, not more tablets.

• Free and combined chlorine measured separately
• pH and alkalinity adjusted together so they hold
• Stabilizer measured, and drained down when it's too high
• Calcium hardness checked to protect plaster and tile
• Phosphates tested when algae keeps returning

What Florida does to pool water

Afternoon storms dump rain that's slightly acidic and carries whatever was in the air, which in spring means oak pollen by the pound. Rain dilutes the chlorine and the stabilizer, drops the pH, and adds organic load all at once. A pool that was perfect on Monday can be off by Thursday.

The sun does the rest. UV burns off unprotected chlorine in a few hours. That's why a pool that gets shocked and then left alone is green again in a week. Balancing here means keeping the stabilizer in the right range so the chlorine you pay for actually lasts.