Understanding Chlorine

What Chlorine Does

Chlorine serves two critical functions in your pool:

Sanitization: Kills bacteria, viruses, and other pathogens
Oxidation: Breaks down organic contaminants like sweat and sunscreen

Without adequate chlorine, your pool becomes a potential health hazard. With too much, swimmers experience eye and skin irritation.

Understanding Chlorine Readings

Free Chlorine

This is the chlorine available to sanitize — the number that matters most. Target: 1-3 ppm for residential pools.

Combined Chlorine

Chlorine that has reacted with contaminants and is no longer effective. If you smell a strong "chlorine smell," you actually have too much combined chlorine. Target: under 0.5 ppm.

Total Chlorine

The sum of free and combined chlorine. If total is much higher than free chlorine, you have a combined chlorine problem requiring shock treatment.

Why Chlorine Levels Fluctuate

Sunlight: UV light destroys chlorine (stabilizer helps)
Bather load: More swimmers = faster chlorine consumption
Temperature: Warmer water uses chlorine faster
Organic debris: Leaves, pollen, and dirt consume chlorine
Algae: If present, consumes chlorine rapidly

Chlorine Delivery Methods

Tablets (Trichlor)

Slow-dissolving, but adds stabilizer over time. Acidic.

Granular

Fast-dissolving, good for shocking. Dichlor adds stabilizer.

Liquid Chlorine

Fast-acting, no residue. Raises pH. Professional choice.

Salt Generators

Creates chlorine from salt. Consistent but raises pH.

When This Becomes a Service Issue

Contact a professional when:

Chlorine will not hold (drops rapidly after adding)
Combined chlorine is high (strong smell)
Stabilizer is over 100 ppm
Algae has developed
Equipment malfunction (salt cell, chlorinator)

Frequently Asked Questions

What is the ideal chlorine level for a pool?

For residential pools, maintain free chlorine between 1-3 ppm. For pools with heavy use or vacation rentals, aim for 2-4 ppm.

Why does my pool smell like chlorine?

A strong chlorine smell usually indicates combined chlorine (chloramines), not too much chlorine. This happens when chlorine reacts with contaminants. The solution is often to shock the pool to break down the chloramines.

How often should I add chlorine?

This depends on your pool size, bather load, and weather. Test your water 2-3 times per week and add chlorine as needed to maintain 1-3 ppm. Salt pools generate chlorine continuously but still need monitoring.