Vac-to-waste after complexing with aluminum sulfate (alum).
Water conservation has been in the spotlight as the result of drought conditions affecting various parts of the country from year to year. In an effort to be responsible for the conservation of this valuable resource, onBalance has been investigating various ways the pool and spa industry can help reduce unnecessary water loss.
In the water chemistry standard, it is recommended that pools be drained if the…
- Total Dissolved Solids (TDS) exceeds 1500 ppm over the starting point
- Total Calcium hardness (TC) exceeds 1000 ppm
- Cyanuric Acid (CyA) exceeds 100 ppm
Focus on the Target — One way the industry could point our members toward conservation would be to change the primary recommendation from "drain the pool" to "lower the concentration" of the out-of-range constituent in the water. This would focus the operator on the fact that there are often other legitimate alternatives to draining. As applicable, these alternatives could then be listed.
Demo Pools with complexed melamine cyanurate.
Total Dissolved Solids — In the early 1990s, we beta tested and then purchased and operated what may have been the first reverse osmosis/nanofilter purpose-built for the pool industry, and reported on our results in the trade press and in the Journal of the Swimming Pool and Spa Industry.
This alternative to draining a pool filters to the nano — rather than the micro-level. Although as much as 10% of the water may be lost (rejected as brine) in the process, the other 90% can be softened to recommended levels. In addition to TDS, metals, minerals, salts, disinfection byproducts and other undesirable solubilized compounds are also removed.
Calcium Hardness — Another way of reducing calcium hardness in pool water (in addition to nanofiltration) is to precipitate the calcium by "dumping" sodium carbonate (soda ash) in the pool, and then filtering out the resultant calcium carbonate precipitate using a DE filter. This "lime softening" process is capable of lowering calcium hardness down to about the 300 to 400 ppm level while slightly lowering the pH and alkalinity. (See https://bit.ly/OnBalanceEducation and https://bit.ly/FixMilkyWater for more information.) This process only removes calcium hardness, not TDS.
Hyperchlorination method.
Cyanuric Acid — There are also methods to remove cyanuric acid from pool water without draining a pool. These methods include nanofiltration, polymer skimmer pillows and activated organism additives. We have also been successful removing cyanuric acid in our demo pools using alum flocking, melamine complexing and hyperchlorination (see https://bit.ly/CYARemoval and the OnBalanceEducation link above). Our industry does not need to endorse or even recommend any of these methods. However, we can and should recommend cyanuric acid reduction. We can then inform the operator that draining, nanofiltration, or the various other chemical applications are available to lower the cyanuric acid concentration.
Laboratory testing of methods.
It is our hope that a mention of alternatives to draining for calcium hardness and cyanuric acid buildup will inform service techs, operators, pool owners and regulatory entities that there are viable methods of lowering these soluble compounds while respecting water usage and conservation at the same time.
This article first appeared in the November 2024 issue of AQUA Magazine — the top resource for retailers, builders and service pros in the pool and spa industry. Subscriptions to the print magazine are free to all industry professionals. Click here to subscribe.
