Can Pool Chlorine Make You Sick? Health Effects Explained

How Pool Chlorine Can Make You Sick

High Chlorine Levels (Over-Chlorination)

When free chlorine levels exceed 5-6 ppm, you may experience:

• Skin irritation: Rashes, dryness, and chemical burns
• Eye irritation: Redness, burning, and tearing
• Respiratory problems: Coughing, wheezing, and difficulty breathing
• Hair damage: Dryness, discoloration, and brittleness
• Swimsuit bleaching: Fabric damage and color loss

Contrary to popular belief, that strong "chlorine smell" at pools isn't from too much chlorine - it's actually from chloramines (combined chlorine) formed when chlorine reacts with contaminants like sweat, urine, and body oils.

Low Chlorine Levels (Under-Chlorination)

When free chlorine drops below effective levels, harmful microorganisms can multiply, causing:

• Recreational Water Illnesses (RWIs): Diarrhea, ear infections, and skin infections
• E. coli and Cryptosporidium infections: Severe gastrointestinal illness
• Legionnaires' disease: A serious form of pneumonia
• Hot tub rash (Pseudomonas): Itchy, bumpy skin infection
• Algae-related issues: Slip hazards and bacterial growth

Determining Safe Chlorine Levels

Safe chlorine levels depend on your cyanuric acid (CYA) concentration. Use this FC/CYA relationship:

• CYA 30 ppm: FC should be 1-2 ppm
• CYA 40 ppm: FC should be 1.5-3 ppm
• CYA 50 ppm: FC should be 2-4 ppm
• CYA 60 ppm: FC should be 2.5-5 ppm
• CYA 70-80 ppm (SWG pools): FC should be 3-6 ppm

Target CYA levels of 30-50 ppm for regular pools and 70-80 ppm for salt water generator pools.

Testing and Maintaining Safe Levels

Testing Requirements

1. Test daily during swimming season using a reliable test kit like the Taylor K-2006C FAS-DPD kit
2. Test free chlorine (FC), combined chlorine (CC), pH, and total alkalinity at minimum
3. Test CYA monthly using the Taylor CYA test (R-0013)
4. Test immediately after heavy use, rain, or chemical additions

Adjusting Chlorine Levels

To raise FC: Add liquid chlorine (sodium hypochlorite). Add 1 gallon per 10,000 gallons to raise FC by approximately 1 ppm. Retest after 15-20 minutes of circulation.

To lower FC: Stop adding chlorine and let sunlight naturally reduce levels, or add sodium thiosulfate (chlorine neutralizer) - use 1 oz per 10,000 gallons to reduce FC by 1 ppm.

pH Balance and Chlorine Effectiveness

Chlorine effectiveness dramatically decreases as pH rises:

• pH 7.0: 73% effectiveness
• pH 7.5: 50% effectiveness
• pH 8.0: 23% effectiveness
• pH 8.5: 10% effectiveness

Maintain pH between 7.4-7.6 for optimal chlorine efficiency. Use muriatic acid to lower pH or sodium carbonate (soda ash) to raise it.

Preventing Chlorine-Related Illness

For Pool Operators

• Maintain consistent FC levels based on your CYA reading
• Keep combined chlorine below 0.5 ppm - if higher, shock the pool
• Ensure proper circulation - run pumps 8-12 hours daily
• Clean filters regularly and backwash when pressure rises 8-10 psi
• Address algae immediately with SLAM (Shock Level And Maintain) process

For Swimmers

• Shower before and after swimming to remove contaminants and chlorine
• Don't swim if you have diarrhea - wait until 2 weeks after diarrhea stops
• Avoid swallowing pool water even in properly maintained pools
• Exit the pool if you experience irritation and retest chemical levels

When to Shock Your Pool

Shock when combined chlorine exceeds 0.5 ppm or when dealing with contamination. For SLAM process:

1. Raise FC to shock level (varies by CYA - typically 10-12 ppm for CYA 30-50)
2. Maintain shock level 24/7 until you pass the Overnight Chlorine Loss Test (OCLT)
3. Test FC every few hours and add liquid chlorine to maintain shock level
4. Continue until water clears and FC holds steady overnight

Common Mistakes That Cause Illness

• Relying on smell to judge chlorine levels - strong odors indicate chloramines, not high FC
• Using trichlor tabs as primary sanitizer - these add CYA continuously, eventually making chlorine ineffective
• Not testing CYA regularly - high CYA (over 80 ppm) requires very high FC levels
• Adding shock products instead of liquid chlorine - many contain fillers and don't provide pure chlorine
• Ignoring pH levels - high pH makes chlorine nearly useless

By maintaining proper water chemistry and following TFP (Trouble Free Pool) principles, you can enjoy a healthy swimming environment without chlorine-related illness.

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