What is the proper method for chlorinating well water?

Proper Method for Chlorinating Well Water

The proper method for chlorinating well water involves shock chlorination with a chlorine solution to achieve 1-2 mg/L (1-2 ppm) of free residual chlorine at the tap, followed by flushing the system until chlorine odor is no longer detectable. 1

Shock Chlorination Procedure

Materials Needed

• Chlorine-based product registered by the EPA for water treatment (e.g., sodium hypochlorite/household bleach)
• Water testing kit to measure chlorine levels
• Protective equipment (gloves, eye protection)

Step-by-Step Process

1. Initial Preparation

   • Turn off electric power to the pump
   • Remove or bypass any carbon filters, water softeners, or other treatment systems that might be damaged by high chlorine levels
   • Calculate the volume of water in your well system (well casing + storage tanks + pipes)

2. Shock Chlorination

   • Add enough chlorine to achieve a free chlorine residual of >2 mg/L (>2 ppm) throughout the system 1
   • For heavily contaminated systems, chlorination of the water heater or tank to levels of 20-50 mg/L (20-50 ppm) may be required 1
   • Maintain the water pH between 7.0 and 8.0 for optimal chlorine effectiveness 1

3. Distribution

   • After adding chlorine to the well, run water through each fixture in the house until you detect chlorine odor
   • Maintain the elevated chlorine concentration in the system for >2 hours but <24 hours 1

4. Flushing

   • After the contact period, flush the system thoroughly until no chlorine odor remains
   • Begin flushing from fixtures closest to the well and move outward
   • Direct chlorinated water away from sensitive plants and water bodies

5. Verification

   • Test water to ensure chlorine levels have returned to safe drinking levels
   • For ongoing maintenance, maintain free chlorine residual of 1-2 mg/L (1-2 ppm) at the tap 1

Maintenance Chlorination

For ongoing disinfection of well water systems:

• Cold water: Store and distribute at <20°C (<68°F) 1
• Hot water: Store at >60°C (>140°F) and circulate at a minimum return temperature of 51°C (124°F) 1
• Chlorine residual: Maintain 1-2 mg/L (1-2 ppm) of free residual chlorine at the tap 1

Special Considerations

During Water Emergencies

• If a boil water advisory is issued, bring water to a rolling boil for at least 1 minute before use 1, 2
• After the advisory is lifted, run faucets at full flow for >5 minutes 1

For Immunocompromised Individuals

• Boiling water for at least 1 minute is particularly important during outbreaks of waterborne illness 2
• Consider using only sterile water for oral consumption until water safety is confirmed 1

Monitoring and Testing

• Regularly test well water for:

  • Free chlorine levels (should be 1-2 ppm)
  • pH (optimal range: 7.0-8.0)
  • Bacterial contamination

• Increased monitoring is recommended after:

  • Heavy rainfall
  • Flooding events
  • Repairs to the well system
  • Changes in water appearance, odor, or taste

Common Pitfalls to Avoid

• Insufficient contact time: Ensure chlorine remains in contact with water for at least 2 hours for effective disinfection 1
• Inadequate flushing: Residual chlorine levels that are too high can cause corrosion and unpleasant taste
• Neglecting hot water systems: Clean hot-water storage tanks and water heaters to remove accumulated scale and sediment that can harbor bacteria 1
• Relying solely on chlorination: Recent research shows that building managers cannot solely rely on chlorine as a barrier to mitigate bacterial growth in bulk water, especially in tepid and hot water systems 3
• Ignoring chlorine decay: Chlorine is not stable in pipe networks, with free chlorine having a half-life of approximately 140 minutes in static tests 4

By following these guidelines, you can effectively chlorinate your well water system to ensure safe drinking water and minimize health risks associated with waterborne pathogens.