What is chlorine demand?
Chlorine is a powerful oxidizing agent that will break down many of the undesirable contaminants in a pool. Chlorine demand refers to the situation where it is impossible to maintain proper chlorine concentrations even after repeated application of a chlorinating product. Almost any organic contaminant in large amounts (such as bacteria, algae, ammonia, urine, sweat, health and beauty products, plant material or fertilizer) can contribute to causing a demand.
Unfortunately, there is no easy cure for chlorine demand. In most cases, there are only two options. The first is to add the required amount of chlorinating product to remove the demand and the second is to replace some of the water in the pool. When the demand is also accompanied by very cloudy water, a treatment with a flocculent may help reduce the demand by physically removing some of the impurities from the water.
It is important to recognize that there are two types of contaminants being treated. The first is “fast-reacting”. This includes small molecules that will react with chlorinating agents very quickly. The second type is “slow-reacting”. This includes larger organic based molecules. These larger, slower reacting impurities are usually the result of swimmer waste and can take up to 36 hours to completely oxidize.
For this reason, checking the chlorine residual a few hours after treatment could show the presence of free chlorine, and you might assume the demand is gone. However, if slow-reacting contaminants are present, the chlorine can be used up as they continue to react and residual can later drop to zero, which means that the demand is not truly broken. That’s why it’s very important to add the entire amount of recommended product as instructed, continue to test frequently, and be sure the free chlorine residual holds at 1 – 3 ppm for a full 36 hours.
Prevention is better than cure
Of course, the best course of action is always prevention. Maintaining a program that includes regular oxidation – aka “shocking the pool” – as well as application of a maintenance algaecide will help keep pool water clear and free from contaminants. Most pool care systems recommend a once per week shock application, but there are instances where more frequency is needed. These include heavy bather loads, rain, warmer than normal temperatures, and any time there is suspected contamination of the pool water (such as fertilizer or pollutants). Designing a maintenance program specific to the characteristics of each pool will help prevent problems before they begin.
We’re here to help
If you are concerned about chlorine demand or any other aspect of maintaining your pool, pop by Sunshine Pools and talk to one of our water care experts. They can perform the analysis needed to properly diagnose any issue and recommend the right product and treatment to revitalize your water and get it sparkling clear. If requested, we can also provide on site assistance to bring your water quality up to where it should be, or an ongoing maintenance program to keep it there all pool season!
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