The True Strength of Cholorine
Professional pool service techs have some choices when it comes to chlorinating pools. For many the type of chlorine being used may be based on anything from the make-up of regional source water, storage and safety or cost savings. Liquid sodium hypochlorite (chlorine) or Calcium Hypochlorite Cal-Hypo are both unstabilized forms of chlorine, so they contain no CYA. Trichlor tablets contain cyanuric acid CYA and have a very low pH. Because they are acidic, they will lower both pH and total alkalinity. When choosing a type of chlorine, it is important to understand the by-product that is left behind after chlorination and how this will affect the water and type of pool surface. When it comes to cost savings what really matters is knowing what you are getting for your money.
When evaluating the power of chlorine, we start with elemental chlorine. This is chlorine gas. We use chlorine gas as the standard to measure other types against because it is 100% pure chlorine. Since all other types of chlorine in the pool industry are chlorinating compounds and not 100% pure, we need to determine how much pure chlorine there is in the compound. There can be confusion on this because of chlorine labels and available percentages. One of the most common misconceptions is that liquid chlorine is the weakest type of chlorine because it is only 12.5% available chlorine. And tri-chlor must be the strongest because it is 90% available chlorine. However, when comparing liquid volume percent to dry weight there is a difference. It comes down to pounds of pure chlorine in the compound that you are using. Because it is a liquid when determining the pounds of pure chlorine in 1 gallon of 12.5% sodium hypochlorite it would be 12.5% x 10 lbs. (the weight of a gallon of liquid chlorine) this equals 1.25 lbs. of pure chlorine in one gallon of liquid. Now, let's take the 90% trichlor. It is dry weight, so we take 90% x 1lb. equals 0.9 lbs. of pure chlorine. 65% cal-hypo would be 65%x 1lb. equals 0.65 lbs. of pure chlorine. So, it is the gallon of liquid that has the highest amount of pure chlorine. When it comes to getting the most for the money you spend, liquid chlorine 12.5% is the best cost advantage. And with liquid there are no hidden costs from the build up of excess CYA or calcium that can lead to increased draining or water balance chemicals. Liquid truly does give you the most bang for your buck.