A few questions have been raised in the pool industry recently about pool water treatment. These include whether trichlor is inherently bad for pool plaster, what the effect of cyanuric acid is on pool plaster, whether pools can successfully be chemically maintained with weekly service visits, and what, if any, improvements have been made to water balancing chemistry in the last 40 years.Trichlor – Because of its ease of use and its stability in storage, trichlor use has increased in popularity. When using trichlor for chlorination, very little if any muriatic acid is needed for pH reduction, as compared to the need to use a significant amount of muriatic acid when using bleach or cal hypo.The advantage of using trichlor over having to add liquid acid (and even dry acid) is that it dissolves very slowly, which allows the water to buffer (resist pH change) the moderately acidic nature of this chemical much easier. Both muriatic acid and sodium bisulfate (dry acid) dissolve quickly, and immediately pack a significant punch in lowering pH. Since muriatic and dry acids are heavier than water, they sink to the bottom of pools when added improperly, which is aggressive to the plaster surface. More importantly, muriatic and dry acids are one hundred times more acidic than trichlor. That is certainly something to be considered. When added by hand, liquid and dry acids should always be diluted and trickled around the perimeter of the pool.Because of the slow dissolving nature of trichlor, another advantage of using it is that it helps maintain a more consistent pH over the course of a week. While treating swimming pool water, we all have learned that the pH in typical pool water generally rises after treatment and balancing. So when service techs balance pH to 7.4 when using liquid bleach and acid, and return a week later to treat the water again, the pH may have risen to as high as 8.0. However, when slow-dissolving trichlor is used for chlorination (instead of bleach or cal hypo), the slow dissolving of trichlor (which is moderately acidic) will offset this natural pH rise over the course of a week and will help maintain a more constant pH during this time period. So as one can see, there are certain advantages of using trichlor.While improperly fed trichlor (that is, when trichlor is allowed to concentrate rather than dissolve in a distributed fashion) can cause etching on a top step or corner of a pool or at a return line opening, blaming trichlor for other, non-etching related plaster problems, especially in other areas of the pool, is misguided.Cyanuric acid – This chemical has come under recent scrutiny – both in its role as a component of the alkaline buffer in a pool, and its effect on plaster. In a nutshell, cyanurate (the alkaline portion of cyanuric acid in water) is part of the total alkalinity. When performing accurate water balance equations (SI), only the carbonate/bicarbonate type of alkalinity is supposed to be included, so the bicarbonate needs to be isolated from the cyanurate alkalinity. The APSP has published material on this process, and we recommend it. On the other hand, some claim cyanuric acid is inherently aggressive to plaster surfaces. Properly dissolved cyanuric acid at recommended pool concentrations is not aggressive, in and of itself, to plaster.Weekly Service – Some industry people have made the claim that service techs are not capable of properly maintaining balanced water chemistry with weekly service visits. In light of the fact that many have been doing that for decades, and absent any proof to the contrary by the claimants, this one doesn’t really deserve further comment, other than to perhaps point out that the increase in automation, the use of Trichlor mentioned above, and the use of cyanuric acid, make this claim even further from the truth.Advances – Let’s look at a few other advancements in the maintenance of pools over the years. Before the mid-70s, test kits usually only included pH and total chlorine tests, while testing for alkalinity and calcium hardness was almost non-existent. Now, test kits, including test strips, are more sophisticated which includes testing for alkalinity, and hardness. Mini spectrophotometers are now available for more reliable readings. Mini labs are available for very accurate titration capabilities.Back in the 1970’s, the concept of water balance (Langelier Saturation Index) was not widely known or understood. Now, balancing water using the Saturation Index is now expected of both professionals and pool owners. Very recently, the Saturation Index has been modified and improved because of high TDS considerations. Chemical addition charts have been developed and improved providing more accurate amounts of chemicals to add for balancing. Computer software programs provide pool stores with the ability to assist pool owners in water balancing.The service industry today has special chemical startup procedures, chelation and sequestering agents, and stain removal programs. Research has shown optimal methods of chemical addition. For example, 15 years ago onBalance published its research demonstrating the fallacy of “slugging” liquid acid into pool water (for extra alkalinity reduction), and more importantly, demonstrated that it is also detrimental to pool plaster. onBalance also improved the accuracy of the original chemical dosage charts published before 1990. Devices have been introduced to slowly add chemicals and the use of automation has blossomed over the last couple of decades. Even greater advancements have come from the development of automatic pool cleaners and more sophisticated filtration systems.There has been an increase in educational seminars throughout the country, teaching and helping service techs to better understand the proper applications and mechanics of water chemistry maintenance. Trade associations such as IPSSA, UPA, APSP, FPSIE, and NSPF, with their courses and requirements for certification have been a major factor in the improvement of overall service quality.In conclusion, the service industry is providing a higher quality of pool maintenance today. We believe that there will continue to be improvements and advancements within our segment of the industry.onBalance is a consulting group comprised of Que Hales, Doug Latta and Kim Skinner
Here in Dallas, many service companies I know switch to cal hypo once the water temps get low enough not to need the constant feed of dissolving trichlor tabs. Together with normal backwashing, spring rains and tile line drains, we keep our stabilizer levels pretty much in check. True, on some of our cartridge filter pools, we have to dilute every now and then to keep it within recommended levels. But not as much as you would think for pools that get a steady diet of trichlor 9 or 10 months of the year. I've seen the difficulties in maintaining overstabilized pools and it's not worth the effort when all you have to do is drain a couple of feet of water off the pool every now and then.
As far as stabilizer being called out for plaster damage, pretty much the only folks who are pushing that line are those who sell competing products or alternative sanitizers. Not what you would call an unbiased research entity.
Thank you for providing good reasons not to use trichlor exclusively and year around, especially during winter months. I want to reiterate (to all readers) that trichlor is not inherently bad for plaster pools. It is not as acidic as muratic acid and dry acid, and the alkaline nature of typical pool water will neutralize (buffer) and offset the slow dissolving and acidic trait of trichlor. Floaters do need to be prevented from "sticking" on top steps. Just don't let someone blame trichlor for what may be a plaster defect and is not water chemistry related.
Bruce, I need to check out the Taylor correction chart. Sounds interesting.
Kim,
I always look forward to your blogs and sometimes lively debate.
In general, isn't seperating cyanurate alkilinity from bicarbonate alkilinity a bit cumbersome in the field? Taylor includes a very user friendly correction factor in their test kit that I have found easy to teach to techs and homeowners alike.
On another note. Across much of the southern US we do not winterize our pools and during the cold months I recommend not using trichlor. Instead, change to weekly additions of unstabilized chlorine. There are at least two considerations: 1) On the lowest setting a tablet feeder will overchlorinate the pool, 2)On the lowest setting a tablet feeder will not be protected from freezing.
Twelve months of feeding stabilized chlorine will put CYA levels off the chart. Reducing the trichlor feed to only the warm months mitigates the overaddition of CYA.
Comments
Here in Dallas, many service companies I know switch to cal hypo once the water temps get low enough not to need the constant feed of dissolving trichlor tabs. Together with normal backwashing, spring rains and tile line drains, we keep our stabilizer levels pretty much in check. True, on some of our cartridge filter pools, we have to dilute every now and then to keep it within recommended levels. But not as much as you would think for pools that get a steady diet of trichlor 9 or 10 months of the year. I've seen the difficulties in maintaining overstabilized pools and it's not worth the effort when all you have to do is drain a couple of feet of water off the pool every now and then.
As far as stabilizer being called out for plaster damage, pretty much the only folks who are pushing that line are those who sell competing products or alternative sanitizers. Not what you would call an unbiased research entity.
Bruce, I need to check out the Taylor correction chart. Sounds interesting.
I always look forward to your blogs and sometimes lively debate.
In general, isn't seperating cyanurate alkilinity from bicarbonate alkilinity a bit cumbersome in the field? Taylor includes a very user friendly correction factor in their test kit that I have found easy to teach to techs and homeowners alike.
On another note. Across much of the southern US we do not winterize our pools and during the cold months I recommend not using trichlor. Instead, change to weekly additions of unstabilized chlorine. There are at least two considerations: 1) On the lowest setting a tablet feeder will overchlorinate the pool, 2)On the lowest setting a tablet feeder will not be protected from freezing.
Twelve months of feeding stabilized chlorine will put CYA levels off the chart. Reducing the trichlor feed to only the warm months mitigates the overaddition of CYA.