How to Reduce Combined Chlorine in a Pool?

To reduce combined chlorine (also known as chloramines) in your pool, you primarily need to shock the pool water. Here's how:

Understanding Combined Chlorine

Combined chlorine forms when free chlorine reacts with organic matter (sweat, urine, leaves, etc.) in the pool water. This creates chloramines, which are less effective sanitizers and are responsible for the chlorine odor and eye/skin irritation commonly associated with pools.

Methods for Reducing Combined Chlorine:

1. Superchlorination (Shocking with Chlorine): This is the most common and effective method. It involves raising the chlorine level significantly to break down chloramines.

   • How it Works: A high dose of chlorine (typically 5-10 times the normal level) oxidizes the chloramines, converting them into nitrogen gas and other harmless byproducts.
   • Procedure:
     • Test your pool water to determine the combined chlorine level.
     • Calculate the amount of shock needed based on your pool's volume and the desired free chlorine level. Aim for a breakpoint chlorination level, which is typically around 10 ppm (parts per million). Consult a pool calculator for precise measurements.
     • Add the shock to the pool according to the manufacturer's instructions (usually pre-dissolving the shock in a bucket of water before adding it to the pool).
     • Run your pool pump for at least 8 hours (preferably 24 hours) to circulate the water.
     • Retest the water to ensure the combined chlorine level has dropped significantly (ideally to 0 ppm). You can swim once the free chlorine level returns to the recommended range of 1-3 ppm.

2. Non-Chlorine Shock (Potassium Monopersulfate): This option oxidizes chloramines without adding more chlorine.

   • How it Works: Potassium monopersulfate breaks down chloramines into their constituent parts.
   • Procedure:
     • Test your pool water to determine the combined chlorine level.
     • Add the non-chlorine shock to the pool according to the manufacturer's instructions, calculating the amount based on your pool volume.
     • Run your pool pump for adequate circulation, as specified by the product instructions.
     • Retest the water. Unlike chlorine shock, you can usually swim shortly after using a non-chlorine shock, as long as the oxidizer level is within acceptable parameters outlined in the product instructions.
   • Important Note: While effective at reducing chloramines, non-chlorine shock doesn't sanitize the water like chlorine shock. Therefore, it’s often used as a supplement to regular chlorination.

3. Supplemental or Secondary Sanitation: These systems help prevent chloramine buildup by reducing the amount of organic matter that reacts with chlorine.

   • Types:
     • UV Systems: Ultraviolet (UV) light destroys organic contaminants and chloramines.
     • Ozone Generators: Ozone (O3) is a powerful oxidizer that breaks down organic matter.
     • Mineral Systems: Mineral sanitizers (like silver and copper) inhibit bacteria growth, reducing the demand for chlorine.
   • Benefits: These systems can significantly reduce the reliance on chlorine and minimize chloramine formation, leading to better water quality and less irritation.

Preventative Measures:

• Regularly shock your pool: Even if combined chlorine levels are low, shocking regularly helps maintain water quality.
• Maintain proper water balance: pH, alkalinity, and calcium hardness all affect chlorine's effectiveness.
• Encourage swimmers to shower before entering the pool: This reduces the amount of organic matter introduced into the water.
• Keep the pool clean: Regularly skim the surface and vacuum the pool to remove debris.
• Ensure adequate circulation and filtration: This helps remove organic matter and distribute chemicals evenly.

By implementing these strategies, you can effectively reduce combined chlorine levels in your pool and enjoy a cleaner, more comfortable swimming experience.