What causes a Chlorine Demand in pools?

Chlorine demand is likely caused by a combination of different types of contaminants

Treating chlorine demand can seem overwhelming, especially if the demand is large. During treatment it is important to recognize that there are two types of species being treated. The first is “fast reacting”. This would include small molecules such as ammonia. As discussed above, ammonia reacts with hypochlorous acid very quickly and is easily oxidized. This fast reacting material enters the pool through rain, source water, bathers and other contamination such as fertilizer

Many times, the contributors to chlorine demand are much more complicated. This brings the discussion to the second type of contaminants, which are “slow reacting”. This includes larger molecules like amino acids and proteins. These molecules are typically very complex; therefore, they require more time to oxidize. These larger, slower reacting contaminants are usually the result of swimmer waste such as sweat or urine and can take up to thirty-six hours to completely oxidize.