Commercial pools have seen their share of transformations over the years as pool designers, builders and operators update and innovate, working to attract and accommodate an ever-evolving audience. But no amount of exciting attractions, comfortable amenities or diverse programming options can overcome poor air or water quality at an aquatic facility. Therefore, priority number one for overseers of these spaces must be providing optimal air and water quality for users and staff, to keep visitors safe and coming back.
The Council for the Model Aquatic Health Code (CMAHC) is currently leading an air quality study with Purdue University. The nonprofit Association of Aquatic Professionals is also involved, and AOAP Executive Director and CEO Juliene Hefter said, “The results of the research will help the aquatics industry understand real-world design and operational issues and how best to address them to ensure safe air quality measurements.”
CMAHC Technical Director Dewey Case said a lot of interesting insights are already coming out of the study, and while it’s not “sexy” work, he pointed out why it’s key work, using competitive swimmers as an example: “How many of those athletes develop pulmonary disease as a result of poor air? What’s the annual dollar amount spent on healthcare because of poor indoor air? Those are high stakes, and we, as an industry, owe it to our swimmers to not take guesses—no matter how educated or experienced—with regard to what’s in our pool air.”
Chloramines are a type of combined chlorine that can form in pool water when chlorine reacts with contaminants—primarily from body waste that swimmers introduce—and then off-gas into the air above the water. Particularly indoors, chloramines can cause unpleasant odors, eye and skin irritation, and respiratory problems, as well as contributing to the corrosion of metals in the facility.
“If a facility has great air circulation and the chemicals are properly maintained at the appropriate levels, chloramines can be controlled,” said Hefter. “In the past, many facilities attempted to find Band-Aid type responses to help rid the water of chloramines. Now there are systems that can assist with this, such as UV, ozone, and chloramine source capture exhaust systems designed to improve indoor air quality in aquatic facilities.”
Chloramine source capture exhaust systems are designed to minimize levels of airborne chloramines and disinfectant byproducts (DBPs). “We know that chloramines are four times heavier than air, so they hover just above the pool, in the breathing zone,” explained Mark Hines, vice president of sales and marketing for a South Carolina-based manufacturer of commercial pool equipment. He said the idea behind their low source capture system “is to collect the chloramines as they develop at the pool and evacuate them out of the building before they can build up.”
There are different installation options for the exhaust systems, and Hines said the wall-mount and bench systems are typically used in retrofit projects while gutter and deck drain systems are more standard on new builds, though they can be used on rehabs, “but it does require tearing up the deck to run ducts and plumbing. It’s always preferable to have the low source capture as close to the edge of the pool as possible, collecting the chloramines before they can go anywhere, so the gutter (system) is the best option.”
Hines pointed out that coordination between the source capture system and a facility’s HVAC system is important, whether on new builds or when replacing dehumidification systems, and he offered some other advice for maintaining good air quality: a well-designed fresh air system that washes walls and windows and creates a sweep across the pool, pushing air toward the source capture system; returns in the walls six feet high or above; good water quality; swimmers showering before they enter the pool; bathroom breaks for kids and swim teams; a clean deck and deck equipment; and keeping cleaning chemicals away from the deck.
Matt Cappello, director of design for Landmark Aquatic, said that he’s found source capture exhaust systems to be helpful. “It’s crucial that there’s coordination of design efforts between the architect and aquatic and mechanical engineers early in the design, as well as the HVAC/DH and source capture exhaust system manufacturers to confirm building design with ductwork.”
Cappello added that communication between the aquatic designer and mechanical designer regarding pool design and features is critical, in that moving water adds substantially to “the latent heat load (water vapor) within the space.” Moving water can be from in-deck/above-deck spray features, waterslides, aquatic play units, lazy rivers, wave pools and surf machines. “Understanding the location of the features and their respective flow rates aids the mechanical designer in the HVAC/DH system design to effectively size the unit as well as locate ductwork to push the humid and chloramine-laden vapor out of the space.”
He added that aquatic and mechanical designers and facility operators should agree on desired temperature and humidity levels, as air flow and velocity from supply to return is important for successful HVAC/DH system design. “Air flow that’s too slow may not effectively push the harmful vapor out of the space, and if too fast will cool the bathers.
“Bringing in outside air is a critical factor in diluting the humid and chloramine-laden air within the space,” continued Cappello. “As such, the exterior environmental conditions in which the outside air is being introduced into the natatorium play a large role in the system design in maintaining the appropriate indoor air temperature and humidity balance.”
Additionally, Cappello said that supplemental water sanitizing systems such as UV, ozone or zeolite and activated carbon filters help address the “water side of the good air quality equation. These strategies help minimize the off-gassing of chlorine from the pool water due to the organics introduced to the pool, spa or splash pad.”
He added that another part of the healthy natatorium equation is the “pool operator maintaining water equilibrium by keeping a neutral pool water Langelier Saturation Index (LSI).”
Case agreed that “The source capturing products are absolutely helpful; it’s really an elegant solution. They’ll help any aquatic venue struggling with poor indoor air quality, but when integrated into the air handling system in the design phase, that’s where these systems really shine.”
Case said that HVAC systems are critical in achieving optimal air quality, particularly systems designed with source capturing in mind and systems designed to maximize air replenishment. “We’re in this strange place where a very high—and rightfully so—emphasis is being placed on being good stewards of this earth and our natural resources. But in the pursuit of energy efficiency, we may be accidentally creating conditions where poor indoor air quality will thrive in our natatoriums.”
Case mentioned computer modeling—Computational Fluid Dynamics (CFD)—as another key tool. “It adds cost to a project, but it’s much better to spend a few extra dollars to ensure proper flow than to have a building with dead zones because the HVAC company just put the ventilation system where they thought it should go. It’s much more expensive to tear out ductwork and rebuild it than it is to run CFD modeling on the front end.”
Another potential solution that Case has recently heard discussions on is the use of surge tanks. “There is some merit for, when a facility uses a surge tank, installing a blower and a vent to the outside. It seems the agitation of the blower broke the surface tension and allowed chloramines to vent to the outside air.” He said that while there’s more to the engineering than simply popping a blower on the surge tank, it’s a “beautiful concept that has shown merit.”
Case also pointed to bather hygiene. “If the bathers simply rinsed instead of a soap shower, that would make a tremendous difference. And most of all, don’t pee in the pool! For competitive pools, simply having swim coaches—however begrudgingly—institute practices that allow for swimmers to get out of the pool to pee would make a serious dent.”
Another key step to good indoor air quality is a secondary treatment system like UV, ozone, or advanced oxidation process (AOP), according to Case, who said these systems “can really help reduce chloramines.” But he added that they need to be sized properly, which can be expensive, and they take maintenance. “They’re not an ‘install it and forget it’ type thing.”
Hefter said they’ve seen more facilities using secondary disinfection in recent years. “UV and ozone systems are effective at killing microorganisms, including chlorine-resistant pathogens like cryptosporidium. UV systems are particularly good at destroying microorganisms, while ozone systems are effective at oxidizing contaminants and reducing chloramines.”
“Supplemental sanitizers, such as UV, ozone, chemical enzyme additives, and hydroxyl-based AOP systems provide a means to not only kill chlorine-resistant bacteria and viruses but also maintain appropriate levels of combined chlorine,” said Cappello, who pointed out a distinction between secondary and supplemental disinfection: “Secondary disinfection for aquatic equipment provides an additional claim over supplemental disinfection that it can meet the cryptosporidium inactivation claim per NSF Standard 50.”
Secondary disinfection systems are far more common indoors, though it’s “usually recommended on outdoor splash pads and spray features,” said Hines.
Added Cappello, “especially in pools and splashpads that aerosolize water through the features, to kill waterborne bacteria and viruses. In fact, several state codes and the MAHC are mandating their use for splash pads that recirculate water.”
Of course, good pool filtration is ground zero for maintaining water quality. “Filters remove debris and contaminants, preventing cloudiness, bacterial growth and imbalanced water quality,” said Hefter, who added that proper filtration also helps sanitizers work more effectively by reducing the organic matter that can consume them. “Ensuring that your filtration system is appropriately sized for the capacity of the pools within your facility is crucial.”
Ensuring that your sanitizer and pH adjuster are appropriately chosen based on the makeup of your source water is also imperative, according to Hefter, to ensure they’ll work efficiently and effectively. “Too many facilities aren’t set up appropriately to work with their source water, and this causes excess expenditures on additional chemicals and adjustments.”
“A clear pool is easier to lifeguard,” said Hines. “Good water quality is better on the skin, hair and swimsuits of swimmers,” and it helps pool plaster last longer and stain less.
He said filter choices come down to the facility and budget. “Regenerative media filters (RMF) have a higher upfront cost than fiberglass sand filters but tend to be less expensive to operate over time. The water, chemical and heat savings of (RMF) can be significant.” Other considerations include pool size, pool use, backwash restrictions and owner preference, according to Hines.
Cappello mentioned the “usual suspects” for filtration choices: cartridge, vacuum or pressure sand filters, and vacuum or pressure RMF, which could be diatomaceous earth (DE) or perlite. “Cost impact from lowest to highest would be cartridge, sand and then regenerative media. Equipment room space impact from smallest to largest would be regenerative media, sand and cartridge. Filter efficacy from lowest to greatest in terms of capturing particulate in microns is rapid rate sand filters at 50 microns, high-rate sand filters at 25 microns, cartridge filters at 15 microns and regenerative media at four to five microns.” (Courtesy of the National Swimming Pool Foundation Pool and Spa Operator handbook.) “Wastewater volume from smallest to largest is cartridge, regenerative media and sand filters.
“Cartridge filters in our experience are the least used systems in commercial aquatics due to space constraints and operational effort to clean and maintain the pleats,” continued Cappello. He said the most frequently used filters in the industry have been pressure sand due to cost, but added that there’s been a “push to pressure RMF for the substantial space and water savings, as well as efficacy.”
And while price has been a limiting factor for RMF, the “price differential with sand filters has decreased significantly” due to increased market competition.
“Other strategies recently seen in commercial aquatic filtration have been additives such as zeolite, activated carbon, flocculants and glass to enhance efficacy, absorb organics such as ammonia and reduce backwash wastewater,” said Cappello.
When choosing a water filtration system, Dewey stressed making sure you have the right company designing your system, “one that specializes in designing commercial pools and, preferably, one that doesn’t have a financial stake in any particular piece of equipment.”
Additionally, he said to consider what the venue can handle. “If the venue has a revolving door of staff, maybe a regenerative DE filter wouldn’t be a great choice from a maintenance perspective. Maybe a properly sized and designed sand filter is a better choice. The best system in the world will perform poorly if the operator doesn’t understand the concepts.”
Dewey also mentioned the importance of maintaining consistent water chemistry, including “keeping pH values between 7.0 and 7.5 to maximize hypochlorous acid (HOCI) formation to ensure top-notch disinfection; and keeping appropriate and consistent chlorine levels. These are all the most inexpensive methods to help reduce chloramine formation.”
Paul Nehlen is president and CEO of a Delavan, Wis.-based company specializing in regenerative media filtration systems. He said their filters were designed with the purpose of filtering water at a higher rate than other filters. “We achieve that with our NSF 50 listing at 3.0 gallons per minute per square foot of filtration.
“Because our filters have been certified to a higher filtration rate,” Nehlen continued, “it’s proven that we can filter smaller particles, which indeed removes particulate matter and biowaste that improves the efficacy of the chemical systems tasked with improving the sanitation of the water, and ultimately the air quality for the swimmers or spectators.”
He explained that more particulate translates to more chemicals and a higher probability of chemical imbalance you can smell in the air in the form of chloramines.
Pool gutters, grating and deck drains also play a part. “In general, a gutter pool that collects water around the entire edge of the pool is going to provide better water quality than a skimmer pool collecting water only in certain areas,” said Hines. And gutter grating that allows for good flow and can be removed to make sure the gutter trough stays clean is important. Additionally, “A deck sloped correctly to make sure dirt and debris on the pool deck is collected in the deck drain is important so that it stays out of the pool.”
Newer technologies including automated chemical controllers have been making it easier to control and monitor air and water quality. Cappello explained that these units can be simplistic in terms of monitoring pool water pH and ORP (oxidation reduction potential), to units that can monitor temperature, free chlorine, total chlorine, total alkalinity, TDS (total dissolved solids), turbidity, flow rate and interfaces for heaters, filter backwash, autofill, UV system and chemical inventory management. “The chemical controller selection should be matched with the comfort level and skill of the facility operator.”
Cappello said they’ve seen several companies offering service contracts for remote monitoring services of aquatic facilities to assist the operators in maintaining optimal pool water chemical levels and air quality as well as the pool and HVAC equipment. “These maintenance agreements can significantly enhance the lifespan of the pool and HVAC equipment as well as the building itself.”
And fundamentals should not be overlooked. “A clean deck and equipment, regular vacuuming of the pool, and power washing the deck, gutter and deck drains regularly all lend a hand in allowing for clean water and better air quality in the pool environment,” said Hines.
Cappello agreed that maintenance, cleaning and proper facility management are essential. “Daily monitoring and recording of water and air quality through maintenance and operation—to report any issues and not ignore them—is critical in the longevity of the building and equipment, as well as bather, lifeguard, spectator or coach comfort, providing a safe and healthy environment that will bring people back again and again.” RM