Pool Care

Chlorine Demand is a pool water chemistry topic that is getting more attention due to changing climates, consumer's water chemistry and understanding of the problem. It is also becoming a greater issue in many private & commercial pools.

Chlorine Demand is defined as "the quantity of chlorine reduced or converted to inert or less active forms of chlorine by substances in the water." Faust and Aly's Chemistry of Water Treatment further state that, "since chlorine is a non-selective oxidant, almost any substance in the water...will react and consume chlorine." In other words, the more "stuff" dissolved in the pool water, whether organic or inorganic; chemical, vegetable or mineral; heavy, constant rainfall can cause a chlorine demand. Or more simply stated, not being able to successfully maintain a chlorine residual following a chock treatment. Certain household cleaners that are not specifically formulated for in-pool-water use will add components such as phosphates or nitrates will interfere with the pool's sanitizer causing a chlorine demand.

Another cause that may prove suspect, at least in our line of thinking, is the Chloramine issue. As you remember, chloramines are chlorine molecules that are chemically linked up (we call them contaminated) with organic waste such as nitrogen, ammonia, etc. More & more local water treatment authorities are using chloramines to sanitize the drinking water supply these days. Chloramines are pretty effective in killing pathogens in the drinking water supply. However, chloramines are not effective oxidizers. You've probably noticed a regular pink line in your home sink, shower or toilet bowl, especially over the past 4 to 5 years. Those spots need more regular cleaning. That's the same pink slime that is in your swimming pool!

Chloramines are used because they are pretty effective and less "offensive" to those who want to rid our planet of chlorine. That premise is utter foolishness since you can't ban or get rid of an element! Anyway, as you top off your pool with the garden hose, you're putting more chloramines into your pool every time and aggravating an already serious problem. Please keep in mind that this issue is NOT pertinent to folks with well water (you have your own issues).

A sure sign that your are experiencing a chlorine demand is the inability to maintain a Free Available Chlorine level of about 1.0 to 3.0 ppm for more than a few hours; even after shocking or super chlorinating.

Since 1992, one of the pool industry's top Technical Services Department has gathered a huge amount of data concerning chlorine demand. It appears that the situation has become more widespread each year. Here are some actions (short version) that can help in dealing with Chlorine Demand.

Doing a proper Chlorine Demand Test. Your local pool Dealer should have a Chlorine Demand test station. When determining the ACTUAL Chlorine Demand, it is imperative that the solution & corrective action be accurate. Liken it to jumping across the Grand Canyon, if you miss, you miss!

 

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Courtesy of www.backyardlandscaping.net 

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