Pool Water Sanitizers

Advantages: Low cost, long shelf life (gas loses little of its effectiveness over time) and ability to respond quickly to changes in demand for the chemical, assuming the chlorinator is properly sized. Disadvantages: It is designated as an acutely toxic gas, and is very dangerous to handle. Because of the high toxicity, it is difficult to get local fire marshals and building officials to sign off on using it. If it is approved for use, the safety measures required (i.e., chlorine gas scrubbers and backup generators), are extremely costly.

Saltwater Chlorine Generation Systems

A healthy, virtually chemical-free alternative to chlorine sanitizers is an on-site saltwater chlorine generation system. Non-iodized table salt (sodium chloride) is added directly into a swimming pool. Salt dosing levels typically range from 3,000 parts per million (ppm) to 5,000 ppm. Compared to the salinity of human tears (7,200 ppm) and sea water (36,000 ppm), the concentration in the pool is relatively low and does not leave a salty smell, taste or feel. As saline water passes through a chlorine-generating cell, low electrical currents transform salt into chlorine. Once the chlorine has killed bacteria and other organic compounds, it reverts back to salt, and the process begins again.

Advantages: Reduces or eliminates the need to store and handle chlorine and other chemicals; eliminates the cost of purchasing liquid chlorine; and produces water with a more natural, smooth and silky “soft water” feel, akin to a European spa treatment.

Disadvantages: Relatively high capital and maintenance costs associated with cleaning the chlorine-generating cells every one to three months; replacing the cathodes and anodes on a periodic basis; and the reduced ability of the system to respond to changes in chemical demand. Some pool operators have mitigated this issue by providing a back-up/secondary system, such as tablet chlorine.

Select A System

Many facilities look to the cost of purchasing chemicals as the primary factor in choosing a system. According to a survey of 10, large, commercial swimming-pool chemical suppliers, only one was able to provide a quote for gas chlorine: approximately $1.00 per pound. All of the vendors were able to provide quotes for 12-percent sodium hypochlorite and 50- to 100-pound pails of calcium hypochlorite:

· Liquid chlorine:

Lowest–$1.80 per gallon (Arizona);

Highest–$2.65 per gallon (Colorado).

Average cost per gallon–$2.16

· Tablet chlorine:

Lowest–$1.70 per pound (Texas);

Highest–$2.78 per pound (Northern California).

Average cost per pound–$2.29

At first glance, the costs for both chemicals appear similar. However, one must consider that it takes 1-1/2 pounds of calcium hypochlorite to equal 1 gallon of 12-percent sodium hypochlorite. The actual average cost for tablet chlorine is $3.44 per equivalent unit of sanitizer versus $2.16 for liquid chlorine. As an example, an outdoor 25-yard x 25-meter pool will require a daily average of 16 gallons of sodium hypochlorite and 24 pounds of calcium hypochlorite. Daily costs equal $34.56 for liquid chlorine and $54.96 for tablet chlorine. When deciding what type of sanitizer system to use, it is important to look at the advantages/disadvantages of each, availability of chemicals, initial capital costs and a detailed life-cycle cost analysis for each system. Life-cycle cost analysis should include factors like electricity usage, monthly maintenance and replacement costs for major components. Now that you’re armed with the facts, you can be an RWI “terminator” in no time.

Randy Mendioroz (rmendioroz@aquaticdesigngroup.com) is a Principal with Aquatic Design Group, a Carlsbad, Calif., consulting firm which specializes in the programming, planning, design and engineering of competitive, recreation and leisure-based aquatic facilities. For more information, call (760) 438-8400, or visit www.aquaticdesigngroup.com.

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