Water Conditioning & Purification Magazine

Radon removal system

Thursday, August 15th, 2019

MCIS Trade Group’s AcceL-AerAtor E99 radon water removal system is designed with simplicity in mind. The system is easy to install, operate and maintain. Over 99-percent efficient for the removal of radon from water, it has no expensive solenoid/ball valves or level switches to operate. Features include a differential fill valve system and all built-in components, making this easy to understand and operate and requires no tools for cleaning.
(603) 944-0206

Inland desal guide

Thursday, August 15th, 2019

The first edition of the American Water Works Association’s M69 Inland Desalination and Concentrate Management is now available. This manual presents key issues and challenges of developing inland desalination facilities, including concentrate management and disposal methods. It aims to aid water utilities and industrial facilities in evaluating and adapting inland desalination for water supply needs. The full manual is also available as a PDF download and as a PDF download plus print set.

Engineering guide

Thursday, August 15th, 2019

Elsevier announces Coulson and Richardson’s Chemical Engineering: Particulate Systems and Particle Technology, Sixth Edition by R.P. Chhabra and Basavaraj Gurappa is now available. Volume SA of this book has been fully revised and updated to provide practitioners with an overview of chemical engineering, including clear explanations of theory and thorough coverage of practical applications, all supported by case studies. A worldwide team of contributors has pooled their experience to revise old content and add new content. The content has been updated to be more useful for practicing engineers.

ATP monitoring system

Thursday, August 15th, 2019

Promega introduces Water-Glo, a tool to help water-treatment plant analysts (and other water-critical industries) quickly and reliably detect living microbes present in a sample. The technology offers a rapid, highly sensitive and flexible measurement system for monitoring microbial contamination in fresh, process, sea or wastewater samples. This tool employs analysis and detection reagent combination. Formatted for lab use in a 96-well plate format, the kits and companion instrumentation can quickly analyze ATP levels in up to 90 samples in less than 90 minutes.

DNA-based microbial solutions

Thursday, August 15th, 2019

LuminUltra introduces its GeneCount portfolio of DNA products and services, designed to quantify, specify and target the types of organisms found in all types of water systems, on surfaces and in solid samples. These products and services complement the company’s flagship ATP measurement kits by identifying exactly which organisms are in a sample. Products and services include: GeneCount Quantitative Polymerase Chain Reaction (qPCR) services, testing equipment and kits, which allow users to rapidly screen for specific microbes or groups of microbes/ GeneCount Next Generation Sequencing (NGS) services can identify nearly all types of microbes present, along with insight into what good or harm they may be causing.

UF membrane

Thursday, August 15th, 2019

Toray Membrane USA, Inc.’s HFU-B2315AN pressurized hollow-fiber ultrafiltration (UF) membrane module applies advanced PVDF membrane chemistry and thermally-induced phase separation (TIPS) spinning method that carefully controls the pore size and evenly distributes the number of pores on the membrane surface. The result is a hollow-fiber membrane with fine separation of viruses, bacteria and suspended solids. Low fouling and high permeability help optimize and extend plant performance. Key advantages include tight pore size (0.01 μm); high mechanical tensile strength of hollow-fiber for minimal fiber breakage; chemically-tolerant for operational longevity; high packing density (60 m2) per module, as well as technical support and expertise within reach. This component is tested and certified under NSF/ANSI 61 for drinking-water system components.
(858) 218-2360

The Basics of Healthy Swimming

Thursday, August 15th, 2019

By Kelly A. Reynolds, MSPH, PhD

Swimming is one of the most popular recreational activities in the United States, resulting in over 300-million person visits each year. Recreational waterborne infections (RWIs) have steadily increased relative to some microbial agents. Targeted disinfection at the point of use offers essential solutions for improving swimmer safety.

Problem identification—risk
Treated recreational water venues include swimming pools, spas, interactive fountains, wading pools and dive pools. Each configuration has its own challenges in terms of proper maintenance requirements to maximize public health. Potentially harmful microbes may be shed by infected or colonized individuals and spread to other swimmers through shared water contact. Some of the more common microbial hazards include those that infect through the stomach, such as Cryptosporidium, Giardia, Shigella, norovirus and E. coli O157:H7, and respiratory system, such as Legionella and skin, including MRSA and Pseudomonas. Some of the more common diseases related to treated recreational water venues include acute gastrointestinal illness, diarrhea, skin boils and rashes, eye and ear infections, coughing, wheezing, asthma and others. Symptoms have been linked to both microbial and chemical contaminants spread by ingestion, inhalation or simply having contact with water.

Over the last decade, RWIs associated with swimming pools have been at an all-time high. Focused interventions result in better prevention and management of swimming hazards but outbreaks continue to occur. One study estimated unacceptable risks associated with Cryptosporidium in pools, where annual infection risks are estimated at a probability of 2.6 in 10,000 (generally acceptable risks are less than one per 10,000 persons per year). Children are most at risk with an annual infection probability of one in 100.1 These relatively high risks suggest a need for improved pool maintenance and treatment of resistant microbes to reach public health targets.

RWIs have been formally tracked by the Centers for Disease Control and Prevention (CDC) since 1978. The most recent 2018 report details 493 outbreaks from 2000-2014 in 46 states and Puerto Rico, causing 27,219 cases of illness and eight deaths.2 In about 26 percent of the outbreaks, no causative agent was confirmed but for the remaining outbreaks, 58 percent (n=212) were caused by Cryptosporidium, 16 percent (n=57) by Legionella and 13 percent (n=47) by Pseudomonas. While Cryptosporidium caused the majority of illness (89 percent or 21,766 cases), Legionella caused the most mortality and was responsible for six of the eight associated deaths. More than half (56 percent; n=275) of the outbreaks occurred in the summer months and 32 percent (n=157) occurred at hotel settings.

Although most RWI outbreaks occur in hotel pools and spas, venues associated with the highest level of closures were characterized as child-care pools, followed by hotel/motel and apartment/condominium pools. Interactive fountains and kiddie/wading pools were the most likely to be in violation of state or local pool codes. The smaller amount of water and larger bather-to-water ratio are a challenge for spas and fountains.

Trend analysis provides additional insights into RWIs. For example, from 2000-2006, Cryptosporidium outbreaks increased at a rate of 25 percent per year but then leveled off. Legionella outbreaks, however, continue to increase at a rate of 14 percent per year with the number of cases increasing 286 percent during 2000–2014).2 Reasons for this documented increase are thought to be both increased reporting and awareness and an increasingly aging and immuno-compromised population, as they are more susceptible to these infections.

Pool hygiene
Proper pool hygiene is essential to preventing RWIs. Maintaining water quality can be a difficult task, however, given high bather loads and a host of organic contaminants (i.e., urine, skin cells, sunscreen and natural debris) that increase chlorine demand and reduce residuals to unsafe levels. In 2008, about 12 percent (or 13,532) of routine pool inspections resulted in immediate closure due to the identification of serious public health threats.3 Of these, 12,917 either lacked disinfectant or disinfectant levels were below recommended values. Maximizing disinfectant effectiveness against microbes is dependent not only on adequate disinfectant concentrations but also appropriate pH levels and optimal water circulation and filtration.

Cryptosporidium dominates the list of etiological agents in pools, primarily due to its inherent resistance to chlorine but also because it has a low infectious dose, meaning exposure to only 10 organisms can cause illness, while an infected individual may shed millions of organisms. Even in a well-maintained pool, Crypto can survive for days. Other microbes, like Legionella and Pseudomonas, are susceptible to chlorine but biofilm formation may aid in their persistence. Increased water temperatures, aeration of water, biofilm, scale and sediment all contribute to the growth and persistence of Legionella and Pseudomonas in pools and spas.

Swimmers can help to reduce the spread of RWIs. Persons experiencing symptoms of diarrhea are advised not to swim for two weeks after symptoms have subsided. According to a 2017 survey of 3,114 adults, however, one in four adults would swim within one hour of having diarrhea. Fecal pathogens can be present on our bodies even when we don’t appear to be sick. Thus, showering before swimming is recommended but seldom or never practiced by 52 percent of adults. Unfortunately, swim diapers offer little protection from pre-potty trained toddlers.

Not swallowing water is another control mechanism swimmers have but the fecal-oral transmission route of waterborne microbes is completed given that 60 percent of adults admit to swallowing pool water while swimming. Children have been observed to swallow more than 100 mL of water during each swimming hour.4

Preventing RWIs requires a multi-barrier approach involving bathers and pool operators. The Model Aquatic Health Code (MAHC) was designed to inform both on best practices for healthy swimming.5 Swimmers should shower before swimming and avoid swimming within two weeks of diarrheal illness. Children should be monitored carefully for fecal accidents and taken for frequent bathroom breaks.

Public venues are best operated and maintained by trained staff who adhere to MAHC recommendations. A well-balanced pool typically does not have a strong chemical smell. The smell of chlorine is more likely due to the reaction between chlorine and physical contaminants (urine, feces, sweat, dirt, skin cells, sunscreen, etc.) that produce chloramines. Chloramines can irritate skin, eyes and mucus membranes in the nose and throat as well as cause coughing, wheezing and asthma attacks. Response to finding formed or diarrheal fecal matter in the pool should trigger the following steps:6

  1. Close the venue to swimmers.
  2. Remove as much of the fecal matter as possible using a net or bucket.
  3. Chlorinate the water by maintaining a free chlorine concentration of 2 ppm, water pH of <7.5 for 30 min (or equivalent contact time values; more disinfectant residual may be required if chlorine stabilizers are in use or in water temperatures below 77°F/25°C).
  4. Confirm proper operation of filtration system.
  5. Verify proper maintenance of free chlorine and pH prior to allowing swimmers back into the pool.

Ultraviolet light or ozone systems are added interventions that can effectively inactivate Cryptosporidium and are recommended particularly in venues at increased risk for contamination, such as those frequented by young children.

Assessment of RWIs caused by Cryptosporidium, Legionella and Pseudomonas indicate mixed progress since release of the MAHC. The significant decrease in Pseudomonas and halt in the rise of Cryptosporidium outbreaks suggests the surge in consumer education and standard operator guidelines are having a positive effect. Chlorine-resistant and biofilm-associated pathogens, however, will continue to create challenges in RWI prevention. Continued adaptation of the MAHC among local, state and federal agencies to all treated water venues, along with increased consumer outreach, is needed for sustained benefits.


  1. Suppes LM, Canales RA, Gerba CP, Reynolds KA. “Cryptosporidium risk from swimming pool exposures.” Int J Hyg Environ Health. 2016;219(8):915-919. doi:10.1016/j.ijheh.2016.07.001
  2. Hlavsa MC, Cikesh BL, Roberts VA, et al. “Outbreaks Associated with Treated Recreational Water—United States, 2000–2014.” MMWR Morb Mortal Wkly Rep. 2018;67(19):547-551. doi:10.15585/mmwr.mm6719a3
  3. CDC. “Violations Identified from Routine Swimming Pool Inspections—Selected States and Counties, United States.” 2008. MMWR. 2010;59(19):582-587. https://www.cdc.gov/mmwr/preview/mmwrhtml/mm5919a2.htm. Accessed July 18, 2019.
  4. Suppes LM, Abrell L, Dufour AP, Reynolds KA. “Assessment of swimmer behaviors on pool water ingestion.” J Water Health. 2014;12(2):269-279. doi:10.2166/wh.2013.123
  5. CDC. 2016 Model Aquatic Health Code. 2016. https://www.cdc.gov/mahc/pdf/2016-mahc-code-final.pdf. Accessed July 16, 2018.
  6. CDC. Fecal Incident Response Recommendations for Aquatic Staff. 2018. http://www.cdc.gov/healthywater/swimming/. Accessed July 18, 2019.

About the author
Dr. Kelly A. Reynolds is a University of Arizona Professor at the College of Public Health; Chair of Community, Environment and Policy; Program Director of Environmental Health Sciences and Director of Environment, Exposure Science and Risk Assessment Center (ESRAC). She holds a Master of Science Degree in public health (MSPH) from the University of South Florida and a doctorate in microbiology from the University of Arizona. Reynolds is WC&P’s Public Health Editor and a former member of the Technical Review Committee. She can be reached via email at reynolds@u.arizona.edu

Evaluation of Water Conditioning Devices for Pool and Spa Applications

Thursday, August 15th, 2019

By David Nance

In order to meet market demand, NSF has developed a testing protocol to evaluate various technologies employed as water conditioning devices in pools and spas. This protocol is described in NSF’s Component Certification Specification (CCS), CCS-18325: Water Conditioning Devices for Recreational Water Facilities.

A CCS is a certification guidance document created for materials, components and products that fall within the scope of NSF/ANSI 50, but for which no specific requirements are currently provided. The typical lifespan of a CCS is short, as the testing protocols and evaluation criteria covered by CCS are typically incorporated into NSF/ANSI 50 Equipment and Chemicals for Swimming Pools, Spas, Hot Tubs and Other Recreational Water Facilities within two years from the date when certifications to the CCS are first authorized. Using CCS-18325 as their baseline, the Water Conditioning Device Task Group for NSF/ANSI 50 has worked hard over the last two years to establish a testing protocol and evaluation criteria for water conditioning devices.

Water conditioning devices defined
For the purposes of NSF/ANSI 50 and the work being done by the Water Conditioning Device Task Group, a water conditioning device (WCD) is considered to be any technology or device that, without the use of chemicals, improves the water quality in a pool or spa. Claims of secondary or supplemental disinfection are not covered by the scope of the CCS. A number of technologies and products currently in the market fall within this scope, plus there is the potential for new and innovative technologies and products that could be included in this scope in the future.

Keeping this scope in mind, the test protocol currently drafted by the task group includes guidelines for validating the performance of any product with claims regarding the improvement of the following recreational water quality parameters:

  • Combined chlorine level
  • Chlorine consumption for sanitizer level control
  • Acid consumption for pH control
  • Phosphate level
  • Consumption of water required for circulation system filter cleaning

These evaluations have been developed to establish scientifically valid test results useful for end users to allow confidence and trust in product performance claims, such that they can then pursue the benefits these WCDs offer in terms of lower chemical costs, improved water quality and swimmer comfort, and reduced environmental impact.

Test methodology
Both safety and efficacy of WCDs have been considered as the test methodology for the CCS and subsequently NSF/ANSI 50 have been developed. Safety is evaluated through pressure testing, as well as including requirements for product installation and user information, including warning labels and mechanisms to protect swimmers and operators. Information regarding safety of the water conditioning devices allows facility operators to make informed decisions about product safety, reducing the potential for negative outcomes associated with WCD usage.

Efficacy of WCDs is evaluated in the laboratory, through controlled simulations of real-world conditions. To start the testing, a large volume of clean water is chemically balanced and filtered to obtain standard pool-water conditions. The WCD is then installed and the test water is circulated in a manner mimicking a swimming pool over a minimum period of one week of usage. During the test period, a particulate contaminant load and a synthetic bather load are dosed into the water at regular prescribed intervals. The contaminant load and bather load are intended to simulate the dirt, oils and bodily fluids that typically enter pool water from swimmers under conditions of normal usage.

The test method includes the use of automatic controllers, which monitor and adjust the water to achieve typical pool-water chemistry during the test period. The controllers also measure the amount of chemicals required to keep the water within specifications and the total water volume needed to clean the filtration system. This information is collected and utilized to establish the baseline for water quality and chemical and water consumption. This baseline is then used for comparisons to assess the efficacy of the WCD being tested.

After the baseline is established during a one-week period, the WCD is installed and operated according to manufacturer’s instructions. The baseline conditions are then repeated with the WCD in place and operating with the same data relating to water quality, chemical consumption and water consumption collected by the automatic controllers. The information is collected similarly to the collection of the baseline data. Once the baseline and test periods have been completed, the measured water-quality parameters and chemical-consumption data with and without the WCD in place are compared and assessed against manufacturer performance claims. The WCD must meet minimum reduction requirements established in the protocol and must also meet the manufacturer’s claimed conditioning performance.

Next steps
The proposed test protocol and requirements developed by the task group are currently undergoing review and approval by the NSF Joint Committee on Recreational Water Facilities. This process is expected to continue for a few months and may result in minor changes being made. Ultimately, it is expected that the revised NSF/ANSI 50 will publish by early 2020. Until then, NSF is providing certification of WCDs under CCS-18325.

Meeting market needs
NSF and the NSF Joint Committee on Recreational Water Facilities are continuously working to meet the needs of the industry, of public health officials and of the general public by expanding and updating the requirements and scope of NSF/ANSI 50. Just as technology continues to evolve, so the standard must also evolve to keep pace with it. By developing CCS-18325, NSF created an immediate solution to help stakeholders establish the safety and efficacy of WCDs, plus it provided a springboard for the Water Conditioning Device Task Group to develop criteria to be incorporated into NSF/ANSI 50. These criteria are forward looking, covering not only numerous technologies and products in today’s market, but will also anticipate the development of new products and technologies in the coming years.

About the author
David Nance is the Business Unit Manager for NSF International’s Municipal Water Products and Recreational Water Products and works with NSF’s global testing, auditing and certification services for distribution system components and recreational water products. He has five years of experience in the Recreational Water program. Nance can be reached at dnance@nsf.org or (734) 827-5662.

Changing the Quality of Life with a Quality Water

Thursday, August 15th, 2019

By Donna Kreutz

William ‘Bill’ Siegmund completed his college degree in ethnomusicology and set out to both see and hear by traveling around the world. In the mid-1970s he traveled extensively, backpacking from the southern tip of Africa in Cape Town to Alexandria in Egypt. “Back then it was quite an experience,” he said. That’s when he learned firsthand about the challenges of finding potable water. “There was no such thing as bottled water back then.”

After returning to his home state of Michigan, an investor he knew asked him to share his adventures with a group of friends. “I took down 3,000 slides to less than 100 and did the presentation,” Siegmund said. After that, the investor told him, “You’ve done something few people have ever done. You brought something back with you—what is it?” Siegmund had no idea what the man wanted to know. “Give it to me in a word,” the man said. “Not even a page. One word. What did you bring back?” “I thought about it and finally said ‘water.’ He asked what did that mean? And I replied that the four times I nearly died were all from illness related to water. It was such a trouble on the whole trip to find decent drinking water.”

Siegmund explored water-industry opportunities and established Pure Water Works in Traverse City, MI to sell, rent, assemble and service complete lines of water treatment equipment for residential, commercial and industrial use. “People thought I was crazy. I was living in northern Michigan and the illusion is that the water is pristine pure. Yet some of it is the most challenging. You can drill and have the worst water, then drill 100 feet away and have the best water. So Michigan is a real challenge,” he said.

“In 1976 I formed the business concept. In 1978 I established the first sole proprietorship. In 1980 I opened a store, then incorporated in 1984. Today our residential market covers much of northern Michigan. Our bottled water serves the same region. Our commercial-industrial division works the interstate area. Our Ultra Pure division engineers, builds, designs and installs systems throughout the United States, Canada, Mexico and Brazil,” he said. Major clients include optics giant Zeiss who invented anti-reflecting coating.

“That’s one reason German submarines were so deadly. They had anti-reflecting coating on the periscopes, so there was no reflection off the water. That is where that technology started. We do a lot of work for optical laboratories. When the optical industry switched from glass to plastic, the lenses need to be hard-coated for scratch resistance. Anti-reflective coatings protect eyes from harmful rays of sun. We also do Ultra Pure work for other industries, like the Sherman-Williams paint company. Any aerosol can with a latex product in it is 90 percent water that we make for them. We also get involved in a lot of ozone work. We’re in the process of working with a group of people using ozone as an alternative to pesticides for growing grapes.
“I love the water business. It’s fabulous. There’s so much to learn with the exciting technology available today. We have a certified lab that’s part of the business because we deal with a lot of problem water. We learned early on and coined the phrase application technology, which is applying the correct technology to the specific water problem. We combine technology to get the highest purity of water that is available.

“We just finished a very large project in Tijuana, Mexico for a large manufacturing facility. They had two of our systems in that plant, then called and asked ‘can you build three more?’ The first two had been a real challenge. They had to be able to fit in the door of an airplane to fly from Grand Rapids to Tijuana. This took a lot of problem solving. Another time one of our Zeiss people called and said, ‘we have a huge expansion going on with machines made by the Japanese. The Australians and Germans cannot get them to run.’ We looked at water quality and made a proposal for delivery in 19 days. We were shrink-wrapping the equipment when the truck arrived at our warehouse in Traverse City headed for Grand Rapids for a cargo plane. The entire system had to fit into the aircraft doors with a 79-inch overhead.”

Though Pure Water Works has an international clientele, the company has just 15 employees. “One of reasons we are able to do what we do with a small staff is that we have marvelous service techs excellent at building, installing, even manufacturing, and exceptional support staff who’ve been with us a really long time. It frees me up to be out of the office.” And sometimes that means he’s on the water in his sailboat with his granddaughter.

Siegmund founded the company based on his philosophy of changing the quality of life with quality water. This year Pure Water Works began its fourth decade. “We’re still growing every year by a considerable margin and work to keep that growth going forward.” Training is a core foundation of the company’s success. “We train on a continuing basis and share information in a learning experience. Our water treatment specialists are WQA certified. Our installation service crew members are manufacturer trained. An installation service tech will train with a seasoned crew for a minimum of one year.”

At age 68, Siegmund still travels extensively and had just returned from Utile, Honduras when interviewed for this article. “It’s amazing. People always ask: ‘Where are you this time?’” when he participates in teleconferences for the several WQA committees on which he serves. Siegmund is also involved with the Water Quality Research Foundation. His passion for world travel started early. “In the third grade I would spin the globe and run my finger down to see where to go. When I graduated from college, my grandmother gave me some money, which I quickly turned into travelers checks and took off on trips I’d been planning since I was very young.”

Siegmund continues to be challenged by the water treatment business and his role as Managing Director of Pure Water Works. He said: “I’m an industry-born, self-taught person”—who just happens to have a degree in ethnomusicology. “I still have a large collection. I’ve studied music in India and Africa. That remains a love of my life.”

A Healthy Respect for Pool Chemicals Can Help Avoid Accidents and Injuries

Thursday, August 15th, 2019

By Mary Ostrowski and Robyn R. Brooks

Pool treatment chemicals are essential for safe, healthy swimming pools, but unless used and stored properly, pool chemicals can pose a safety risk themselves. The US Centers for Disease Control and Prevention (CDC) notes the public health value of pool treatment chemicals: “Chlorine and pH, your disinfection team, are the first line of defense against germs that can make swimmers sick.”1 Pool disinfectants destroy a wide variety of germs (e.g., Shigella, norovirus, E. coli 0157:H7 and Pseudomonas aeruginosa) that can cause diarrhea, swimmer’s ear and more serious illnesses.

Acids or bases help maintain appropriate pH for the optimum use of disinfectants. For example, the CT value (concentration of chlorine X contact time needed to destroy Cryptosporidium to a three-log reduction) is about 7,200. If chlorine concentration is raised to 20 ppm, that concentration would have to be maintained for 360 minutes to destroy Cryptosporidium (which causes the majority of outbreaks of acute gastrointestinal illnesses in swimming pools). Giardia is also chlorine resistant but not quite as resistant. CDC’s developing Model Aquatic Health Code will require secondary disinfection (either ozone or UV) to supplement chlorine or bromine primary disinfection in high-risk venues, such as interactive water play areas and wading pools.

Yet, pool chemical accidents are all too common in North America. Almost all accidents involving swimming pool chemicals are preventable. A healthy respect for pool chemicals and knowing a few do’s and don’ts can go a long way toward safer pool chemical use and storage. The following examples describe some of the ways in which pool chemistry can go wrong and how potentially dangerous scenarios can be avoided.

Figure 1. Never store liquids above dry chemicals

Example #1. Avoid mixing pool chemicals
Most pool chemicals are inherently incompatible with each other. Compatible chemicals are chemicals that do not react to any significant extent when mixed at normal conditions. Monochloramine in drinking water is not hazardous, but mixing ammonia cleaners and chlorine-based products is certainly hazardous. Concentration is the key. As a general rule, different pool chemicals should not be mixed. If mixing is required, it should be done exactly according to label directions. Inadvertent mixing and potentially hazard chemical reactions can occur when buckets and measuring tools become contaminated with incompatible substances. Residue of a substance remaining in a container or a scoop could react with other substances with dangerous consequences. Similarly, incompatible chemicals should be stored separately. It is helpful to anticipate what could happen if liquid chemicals leak: would two incompatible products mix? Liquids should be stored low, in a containment tray, to avoid a potentially dangerous scenario.

Chlorine-based products and acids are incompatible and produce chlorine gas when they combine chemically. Exposure to chlorine gas can result in difficulty breathing, even at low concentrations, and may require a trip to the hospital. In February, a Sydney, Australia hotel was forced to evacuate approximately 100 guests and staff2 when the following chemical reaction occurred accidentally:
HOCl + HCl → Cl2 + H2O

Chlorine gas production is particularly vigorous when hydrochloric acid (HCl, also known as muriatic acid) is involved because chlorine gas generation requires the chloride ion. The reaction above is actually an equilibrium reaction, so adding hydrochloric acid to aqueous chlorine solutions drives the reaction to the right, producing chlorine gas. Keep in mind that popular summer drinks such as lemonade and carbonated soft drinks are acids and should not be allowed near pool chemicals.

Chlorine-based products (which form hypochlorous acid, HOCl) and ammonia-based products (e.g., certain cleaning products) are incompatible; these products react to produce hazardous chemicals. In dilute solution, they produce mono-, di- and trichloramine (NH2Cl, NHCl2 and NCl3) respectively, depending upon the chlorine/ammonia ratio, the water temperature and pH.3

i. NH3 + HOCl → NH2Cl + H2O
ii. NH2Cl + HOCl → NHCl2 + H2O
iii. NHCl2 + HOCl → NCl3 + H2O

In swimming pool water at pH 7.0, reaction (i), producing monochloramine, usually is completed within one minute. When the chlorine/ammonia ratio is greater than 5:1, monochloramine reacts to form dichloramine according to reaction (ii). The rate of reaction (ii) is much slower than that of reaction (i). As more chlorine is added, trichloramine forms according to reaction (iii). Trichloramine is the most volatile of the chloramines and is the chloramine most responsible for the strong chemical odor of a poorly managed pool. The reactions above are much faster when concentrated chemicals are mixed. If an ammonia-based cleaner is mixed with an excess of concentrated chlorine-based pool chemical, the reaction product NCl3 (which is explosive at high concentrations) can form rapidly. Even if there is no explosion, NCl3 is very volatile, highly irritating and nearly as toxic as chlorine gas, so a large amount of toxic fumes can be generated almost immediately.

If an excess of an ammonia-based (NH3) cleaner is mixed with a chlorine-based product, such as bleach (NaOCl), one product of the chemical reaction ) is hydrazine, N2H2, which is also toxic and potentially explosive.4

2 NH3 + NaOCl → N2H4 + NaCl + H2O

Even though they may look similar, different chlorine-based products are incompatible with each other. In particular, trichloro-s-triazinetrione (trichlor) should not be mixed with calcium or sodium hypochlorite. If trichlor tablets, which are acidic, are mixed in water with calcium hypochlorite tablets, which are alkaline, they will react as they dissolve. The reaction produces considerable heat and toxic fumes, including chlorine gas. For example, in 2009, an Illinois family tried mixing two brands of pool chlorine in the kitchen, resulting in an explosion. Three members of the family were taken to the hospital with breathing difficulty.5 If the mixture is sealed inside a tablet feeder, the hot gas can produce enough pressure to blow the lid off the feeder or the reaction can be violent enough to blow the feeder apart.6 The labels for both chemical products warn against mixing with other chemicals.

Figure 2. No food or drink in chemical storage areas

Example #2. Never add water to pool chemicals
Last summer, according to an Associated Press report on NJ.com, a hot tub owner in New Jersey was injured as he diluted chlorine7 (presumably a chlorine-based liquid or solid disinfectant or a mixture of disinfectants) with water inside his home.8 A violent reaction ensued and the man was treated for burns to the face and difficulty breathing, according to the media report.

A common way that pool chemicals are mixed improperly is when they are introduced into the water. Pool chemicals should be added directly to the pool; water should not be added to pool chemicals. Adding small amounts of water to a chemical results in a very concentrated solution. If the dissolution process is exothermic (as when water is added to sulfuric acid, for example), so much heat could be released that the product could begin to decompose, leading to additional heat release or gas generation. The solution could boil and splash out of the container, causing chemical burns to the handler. Using proper protocol, the handler adds chemical to the pool, not the other way around. There is a large volume of water in the pool and the resulting solution is very dilute; any heat released is quickly dissipated and insufficient to cause further reaction, vaporization or spattering.9

Inadvertent contact between pool chemicals and water also should be avoided, including: rain water from leaking roofs or broken windows; chemicals in contact with wet floors (chemicals should always be stored higher than the floor); leakage from a fire suppression sprinkler system; hose-down water generated during area cleanup.10 Finally, wet pool chemicals should not be put back into the original containers and sealed. Wet chemicals can slowly react until the reaction accelerates minutes or hours later or dangerous fumes can be generated, exposing the user the next time the container is opened.

Figure 3. Example of improper chemical storage

Example #3. Make sure pool chemical storage areas are well-ventilated, dry and free of combustible and flammable materials
When stored improperly, pool chemicals may chemically decompose, releasing chlorine gas, bromine gas or other toxic substances, which in poorly ventilated areas may corrode packaging, piping, electronics and other metal equipment. Fire is a danger when heat, an oxidizer and fuel combine. Common pool treatment chemicals (e.g., calcium hypochlorite, sodium dichloro-s-triazinetrione, 1-bromo-3-chloro-5,5-dimethylhydantoin, trichloro-s-triazinetrione and potassium monopersulfate) can release oxygen or other oxidizing gases, including chlorine and bromine and chemical packaging (plastic and cardboard) can constitute fuel. That is why combustible or flammable materials, including gasoline, oil, solvents and oily rags, must never be stored near chemicals. Never allow ignition sources, such as barbeque pits, diesel generators, cigarette lighters or gas-powered equipment, such as lawn mowers, motors or welding machines, around pool chemicals.

Oxidizers are not flammable themselves, but they increase the fire hazard because they can increase the intensity of a fire by increasing the rate at which the fuel burns. The National Fire Protection Association classifies oxidizers into four classes (1 to 4).11 A higher class denotes a higher hazard; that is, each higher class increases the intensity of a fire to a greater extent.

Develop a healthy respect for pool chemicals
Pool treatment chemicals provide the benefit of healthy pools for healthy swimming. Untreated or inadequately treated pool water poses unacceptable health risks to swimmers. In the full risk-benefit equation representing the swimming pool system, the pool operator can minimize the risk of chemical accidents by understanding and actively engaging in proper chemical storage and handling. Available pool chemical safety resources include free, laminated chemical safety posters for pool operators, which may be ordered on the CDC website. Additionally, the Chlorine Institute and the American Chemistry Council recently produced a readily accessible You Tube Pool Chemical Safety video that includes messages from CDC. Pool operators can access the video from a computer or smart phone. This summer, help spread the word about pool chemical safety!


  1. Centers for Disease Control and Prevention, Healthy Swimming/Recreational Water. Available: www.cdc.gov/healthywater/swimming/pools/disinfection-team-chlorine-ph.html
  2. “Chemical scare forces guests out of Sydney’s Park Hyatt luxury hotel.” The Australian (February 24, 2014). Available: www.theaustralian.com.au/news/nation/chemical-scare-forces-guests-out-of-sydneys-park-hyatt-luxury-hotel/story-e6frg6nf-1226835934407
  3. Standard for the Operation of Swimming Pools and Spa Pools in South Australia (2003). Government of South Australia. Available: www.health.sa.gov.au/pehs/Swimming-and-recreational-waters/6592%20SAH%20Pool%20Standard_Jun13.pdf (Section 8.2 Chloramines).
  4. Mixing Bleach and Ammonia. http://chemistry.about.com/od/toxicchemicals/a/Mixing-Bleach-And-Ammonia.htm
  5. www.daily-chronicle.com/articles/2009/08/11/03750281/index.xml
  6. Pool Safety. www.achd.net/housing/PoolSafety.html
  7. Many chemicals, including chlorine, often are referred to by an incorrect term. Liquid chlorine (Cl2) is not the same as sodium hypochlorite (NaOCl) solution. Liquid chlorine is stored in pressurized vessels and readily turns to gas at room temperatures. The gas causes breathing difficulty at very low concentrations. Sodium hypochlorite solution (or chlorine bleach), however, is stored in plastic containers and commonly used in pool and household disinfection applications.
  8. “Water-chlorine mixture explodes, burns Surf City man’s face.” NJ.com (August 3, 2013). Available: www.nj.com/news/index.ssf/2013/08/water-chlorine_mixture_explodes_burns_surf_city_mans_face.html#comments
  9. “Why is acid always added to water, and not the reverse?” General Chemistry Online! Available: http://antoine.frostburg.edu/chem/senese/101/safety/faq/always-add-acid.shtml
  10. National Swimming Pool Foundation, (2011). Pool & Spa Operator Handbook.
  11. Buc, E. “Oxidizer classification research project: Tests and criteria,” Fire Protection Research Foundation, Final Report, Nov 2009. Available: www.nfpa.org/research/fire-protection-research-foundation/reports-and-proceedings/hazardous-materials/chemicals.

About the authors
Mary F. Ostrowski has been employed by the American Chemistry Council’s (ACC’s) Chlorine Chemistry Division since December, 2000. As an issues manager, Ostrowski is responsible for chlorine disinfection issues, including benefits promotion, scientific research support and advocating in the regulatory and standard-setting arena for science-based policies. She has worked collaboratively on disinfection issues with public health entities, including the US CDC, the National Environmental Health Association, the Somerset County, New Jersey Department of Health and International Action (promoting safe water for Haiti). Ostrowski holds a Bachelor of Science Degree in chemistry and geology from the City University of New York at Brooklyn College; a Master of Science Degree in geology from Boston College and a Master of Science Degree in environmental management from the University of Maryland’s University College. In addition to her career with ACC, Ostrowski has worked at the Commonwealth of Massachusetts’ Division of Water Resources; as an adjunct lecturer at the University of Maryland’s University College and for a science journal service.

Robyn R. Brooks, Senior Project Engineer, joined the Chlorine Institute (CI) staff in 2012. Prior to joining CI, she worked at The Mosaic Company, Alstom Power and The Dow Chemical Company in operations and engineering groups, where she developed her passion for safety stewardship. Brooks earned a BS Degree in chemical engineering from the University of Tennessee-Knoxville and utilizes her engineering background and industry experience to help advance CI’s safety mission by collaborating with members to review and update safety literature, providing technical and management support to issue teams and working groups and analyzing safety performance data. To support safety outreach, she develops presentations, videos and other safety materials and fields chlor-alkali questions from industry and general public.

Reprinted from Water Conditioning & Purification International, August 2014

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