Appendices for Immediate Closures and Violations Identified During Routine Inspections of Public Aquatic Facilities — Network for Aquatic Facility Inspection Surveillance, Five States, 2013

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Glossary of Terms Used in This Report

“Aquatic facility” means a physical place that contains one or more aquatic venues (e.g., a pool or hot tub/spa) and support infrastructure (e.g., chemical storage area).

“Aquatic venue” means an artificially constructed structure or modified natural structure where the general public is exposed to water intended for recreational or therapeutic purpose. Such structures do not necessarily contain standing water, so water exposure might occur via contact, ingestion, or inhalation. Examples include wave pools, lazy rivers, surf pools, hot tubs/spas, therapy pools, waterslide landing pools, and interactive water play venues.

“Free available chlorine” means the portion of the total chlorine that has not combined with other compounds (e.g., combined with nitrogenous compounds to form dichloramine or trichloramine) and is present as hypochlorous acid (HOCl) or hypochlorite ion (OCl). The pH of the water determines the relative amounts of hypochlorous acid and hypochlorite ion. HOCl is a very effective bactericide and is the active bactericide in the water. OCl is also a bactericide but acts more slowly than HOCl. As pH decreases, more HOCl is formed; however, as pH increases more OCl- is formed. Thus, chlorine is a more effective bactericide at pH =7.8 than at pH >7.8. Free available chlorine concentration must be maintained for adequate disinfection.

“Hot tub/spa” means a structure intended for either warm or cold water where prolonged exposure is not intended. Hot tub/spa structures are intended to be used for bathing or other recreational uses and are not usually drained and refilled after each use. Hot tubs/spas might be used for hydrotherapy and might have air induction bubbles and a recirculation system.

“Interactive water play venue” means any indoor or outdoor installation that includes sprayed, jetted, or other water sources contacting bathers and not incorporating standing or captured water as part of the bather activity area. These aquatic venues are also known as splash pads, spray pads, wet decks, and water playgrounds.

“Pool” means a subset of aquatic venues designed to have standing water for total or partial bather immersion. This does not include hot tubs/spas.

“Wading pool” means any pool used exclusively for wading and intended for use by young children where the depth does not exceed 2 feet (0.6 m).


CDC’s Model Aquatic Health Code

Need for the Model Aquatic Health Code

Preventing aquatic facility–associated illness and injury calls for a strategy that requires at least three key components (known as the three E’s) of environmental health practice: education, engineering, and enforcement. In the United States, individual state and local public health jurisdictions write, enact, implement, and enforce their own unique public health codes covering the design, construction, operation, maintenance, and management of public aquatic facilities; residential aquatic facilities are usually covered under building codes. CDC’s Model Aquatic Health Code (MAHC; is national guidance that can be voluntarily adopted by state and local jurisdictions to minimize the risk of illness and injury at public aquatic venues. The MAHC includes recommendations for education- and engineering-based strategies, and when voluntarily adopted by state and local jurisdictions it also becomes an enforcement-based strategy.


Aquatic facility operators and staff, public health officials (e.g., environmental health practitioners, who inspect public aquatic facilities, epidemiologists, and health communication specialists), bathers, and parents of young bathers all need to be engaged to minimize the risk for aquatic facility–associated illness and injury. Ensuring that each stakeholder knows the steps to take to help prevent aquatic facility–associated outbreaks, drowning, and pool chemical–associated health events is necessary to promoting healthy and safe swimming. To properly operate and maintain public aquatic facilities, operators need training that includes essential topics such as water disinfection and chemistry, mechanical systems (including air handling systems), and other illness and injury risk-minimizing strategies. Studies have found that jurisdictions or public aquatic facilities requiring operator training have fewer violations and better disinfectant concentrations and pH than those jurisdictions or public aquatic facilities without such a requirement (1,2). Environmental health practitioners need to maintain current knowledge about the design, construction, operation, and maintenance of public aquatic facilities and the prevention of aquatic facility–associated illness and injury. Environmental health practitioners sometimes write and enact public aquatic facility codes and always implement and enforce them. Environmental health practitioners enforce design and construction standards through plan review and preoperational inspections, conducted after new construction or substantial alteration, and enforce operation and maintenance standards through routine, complaint, and follow-up inspections.

The aquatics sector and public health should collaborate to disseminate healthy and safe swimming messages to bathers and parents of young bathers. Parents of young bathers are a particularly important group to engage given that young bathers (i.e., those aged <5 years) are a primary source of microbiologic contamination of water in aquatic venues. The aquatics sector and public health should promote healthy and safe swimming year-round, and especially during Healthy and Safe Swimming Week (the week before Memorial Day) and the summer swim season (Memorial Day through Labor Day). This can be done via websites (e.g., and increasingly via social media ( Healthy swimming education campaigns conducted before aquatic facility–associated outbreaks of infectious etiology occur might help prevent them (3). The public needs to understand the potential risks associated with the use of public aquatic facilities and how they can help keep themselves and others healthy (4). Healthy swimming messages for all bathers include: do not swim while ill with diarrhea, do not swallow water while swimming, and shower before entering the water. To promote adoption of healthy swimming behaviors by the public, healthy swimming education campaigns need to dispel commonly held but mistaken beliefs (e.g., that pool water is sterile and that chlorine instantly inactivates all infectious pathogens), which likely lead to swimming with diarrheal illness and thus potential introduction and transmission of infectious pathogens (5). Drowning prevention messages for the public include making sure everyone knows how to swim, fencing off pools to keep children away, using life jackets appropriately, providing continuous and close supervision of young swimmers, and knowing cardiopulmonary resuscitation. The principal pool chemical safety messages for those storing and handling pool chemicals include: secure pool chemicals away from children and read the Occupational Safety and Health Administration– or Environmental Protection Agency–required pool chemical labels, which identify incompatible chemical(s) and personal protective equipment needed for safe handling (


Filtration and halogen (e.g., chlorine or bromine) disinfection post filtration prevent transmission of most infectious pathogens in the water of aquatic venues. Typically, an aquatic venue’s recirculation pump transports the water out of the venue basin via the main drain or other suction outlets, into the venue plumbing, and through the filter to remove particles that can bind with and deplete halogens. The water continues to circulate through the venue plumbing so that the halogen and pH-adjusting chemical (used to optimize inactivation of infectious pathogens and swimmer comfort simultaneously) can be added, diluted, and then mixed. Finally the treated water returns to the aquatic venue via inlets, water jets, or spray features. At CDC-recommended concentrations,* halogens inactivate most infectious pathogens within minutes but the extremely halogen-tolerant parasite, Cryptosporidium, can survive for days (6,7). This means the transmission of halogen-susceptible infectious pathogens (e.g., E. coli O157:H7 or Shigella spp.) can be prevented but the transmission of Cryptosporidium cannot at CDC-recommended halogen concentrations. The emergence of Cryptosporidium as the leading etiology of aquatic facility–associated outbreaks has led to engineering innovations to inactivate (e.g., ultraviolet light or ozone treatment) or remove (e.g., flocculants and improved filter media) the parasite.

Public aquatic facilities can be designed to minimize the risk of drowning. Fencing, walls, and self-closing and self-latching gates and doors can prevent unsupervised entry by young children and unauthorized entry outside operational hours. Aquatic venue design can improve bather visibility for lifeguards and bathers. Additionally, the advent of interactive water play venues, which do not have standing water above ground because the water drains into an underground tank, also minimizes the risk for drowning.

Finally, toxic chlorine gas can be generated if chlorine and acid are not diluted sufficiently before mixing. This can occur when they are mixed by aquatics staff or in aquatic venue plumbing when there is inadequate water flow. When the recirculation pump shuts down or fails to generate adequate flow but the automated chemical feeder pumps continue to inject concentrated chemicals into the water, the mixing of these two concentrated chemicals produces toxic chlorine gas. Restarting the recirculation pump then vents the toxic chlorine gas from the venue plumbing and into the aquatic venue. To prevent this from happening, an electrical interlock should be installed between the automated chemical feeders, the recirculation pumps, and water flow meter/flow switches to shut down automated chemical feeder pumps if the recirculation pumps shut down or there is inadequate water flow in the venue plumbing.


There are no minimum national standards for training aquatic facility operators or comprehensive standards for the engineering of public aquatic facilities to prevent illness and injury. No U.S. federal agency regulates the design, construction, operation, and maintenance of public aquatic facilities, although some federal regulations pertain to specific aspects of public aquatic facilities. For example, the Virginia Graeme Baker Pool and Spa Safety Act (15 U.S.C. §§ 8001 et seq.) aims to prevent main drain–associated entrapment. Individual state and local jurisdictions write, enact, implement, and enforce their own unique public aquatic facility codes, leading to variability in state and local codes. This variability is further compounded by how resource intensive it is to update these codes (e.g., staffing, time, and expertise needed), difficult it is to set standards in the absence of scientific data, and the variability in timeframes within which individual state and local jurisdictions update their codes. Consequently, emerging public health threats (e.g., Cryptosporidium) and aquatics sector innovations, which might pose novel risks for aquatic facility–associated illness or injury or conversely minimize long-established risk, might not be addressed on a timely basis across the United States.

Development of the MAHC

In response to the increasing incidence of aquatic facility–associated outbreaks, particularly those caused by Cryptosporidium, the Council for State and Territorial Epidemiologists, in 2004, called for CDC to hold a national workshop to develop prevention recommendations ( iconexternal icon). In 2005, CDC held the Recreational Water Illness Prevention Workshop for local, state, and federal public health officials and aquatics sector representatives. Workshop attendees identified two barriers to preventing the outbreaks: the variability in public aquatic facility codes across the United States and the resource-intensive effort required to keep each of these codes updated. The workshop attendees’ primary recommendation was for CDC to lead a national consortium of public health officials and aquatics sector representatives to develop an open-access model code, based on the latest scientific data and best practices when scientific data were not available. To maximize the model code’s utility, attendees recommended that the scope be expanded to be an all-inclusive, all-hazards facility–based code that not only aimed to prevent transmission of infectious pathogens but also injury (e.g., drowning and pool chemical–associated health events), as well as poor indoor air quality and other potential adverse exposures at public aquatic facilities. Such a code would cover all of the pertinent aspects of an aquatic facility’s life, including design, construction, operation, maintenance, and management. In addition, attendees recommended developing a companion annex to provide the rationale behind the code, including peer-reviewed, scientific data with references. Individual state and local jurisdictions would be free to voluntarily adopt parts of the model code, revise as needed to meet their unique needs before adoption, or choose not to adopt the model code at all.

During 2007–2014, CDC’s National Center for Emerging and Zoonotic Infectious Diseases and National Center for Environmental Health (with assistance from the National Center for Injury Prevention and Control and the Public Health Law Office) and the New York State Department of Health spearheaded the development of a model code, now known as the MAHC. Soliciting input from the public health, aquatics, and academic sectors was a cornerstone of this multidisciplinary, multi-stakeholder effort. Fourteen MAHC modules ( Box), which included code language and supporting rationale, were drafted by the steering committee or one of 12 technical committees, each with members from the different sectors.

The MAHC steering committee either wrote or reviewed, edited, and approved each draft module in collaboration with the respective technical committee. The 14 modules were posted individually on CDC’s MAHC website for a 60-day public comment period. A total of 2,979 comments on the 14 modules were received; 84.1% (2,504) could be accepted or rejected, of which 76.0% (1,904) were accepted. A total of 13 modules§ were revised on the basis of public comment, and these revised modules were then interwoven into two documents, the code and the annex, and posted for a second 60-day public comment period. The second public comment period allowed reviewers to cross check among modules and ensure consistency throughout the MAHC. Of 1,428 comments, 92.5% (1,321) could be accepted or rejected, of which 63.5% (839) were accepted. Over the two public comment periods, CDC received 4,407 comments and accepted 71.7% (2,743/3,825) of the comments that could be accepted or rejected. Following extensive revision in response to the second public comment period, CDC released the first edition of the MAHC and its annex on August 29, 2014. The MAHC represents the combined work of more than 150 public health, aquatics, and academic volunteers and the many contributors of public comments that helped optimize the MAHC. To keep current with the latest scientific data and aquatics sector innovations, the MAHC will be updated every 2 years through an all-stakeholder–driven process, much like the MAHC development process. The nonprofit organization, the Council for the Model Aquatic Health Code (CMAHC; icon), was created in 2013 and its role is to

  • collect, assess, and relay national input on needed MAHC revisions back to CDC for final consideration for acceptance;

  • advocate for improved health and safety at public aquatic facilities;

  • provide assistance to health departments, boards of health, legislatures, and other partners on MAHC uses, benefits, and implementation;

  • provide assistance to the aquatics sector on uses, interpretation, and benefits of the MAHC; and

  • solicit, coordinate, and prioritize MAHC research needs.

The CDC-CMAHC partnership should ensure that the MAHC remains up to date and continues to minimize the risk for illness and injury at public aquatic venues. In October 2015, the first CMAHC biennial conference was held. CMAHC members subsequently voted on 159 change requests to help guide CDC’s revision of the MAHC prior to the release of its second edition during the 2016 summer swim season.

Tracking Voluntary Adoption of the MAHC

The MAHC is a comprehensive CDC model code that brings infectious disease and injury epidemiology, environmental health, and public health law expertise together to protect public health at public aquatic facilities. The magnitude of the MAHC’s impact on the design, construction, operation, maintenance, and management of U.S. public aquatic facilities is dependent on how many, and which, jurisdictions adopt its recommendations. To track voluntary adoption of the MAHC across the United States, CDC is systematically searching legal databases (e.g., Municode and WestLaw) for changes to public health codes for public aquatic facilities in 20 state and local jurisdictions. The jurisdictions were selected because they had either 1) the highest counts of public aquatic venues and the highest drowning rates (8) or 2) the most aquatic venues per 100,000 persons (9). The searches prioritize recommendations unique to the MAHC that have the greatest potential impact on public health (e.g., requirements for inactivating Cryptosporidium, fencing 6 feet in height, and training on chemical safety for those who handle pool chemicals). The search criteria also include any direct mention of the MAHC or replicated MAHC text.


  1. Buss BF, Safranek TJ, Magri JM, Török TJ, Beach MJ, Foley BP. Association between swimming pool operator certification and reduced pool chemistry violations—Nebraska, 2005–2006. J Environ Health 2009;71:36–40.
  2. Johnston K, Kinziger M. Certified operators: does certification provide significant results in real-world pool and spa chemistry? IJARE 2007;1:18–33.
  3. CDC. Promotion of healthy swimming after a statewide outbreak of cryptosporidiosis associated with recreational water venues—Utah, 2008–2009. MMWR Morb Mortal Wkly Rep 2012;61:348–52.
  4. McClain J, Bernhardt JM, Beach MJ. Assessing parents’ perception of children’s risk for recreational water illnesses. Emerg Infect Dis 2005;11:670–6. CrossRefexternal icon
  5. Beach MJ. Waterborne: recreational water. Cryptosporidium and cryptosporidiosis. 2nd ed. Boca Raton, FL: CRC Press; 2008.
  6. Murphy JL, Arrowood MJ, Lu X, Hlavsa MC, Beach MJ, Hill VR. Effect of cyanuric acid on the inactivation of Cryptosporidium parvum under hyperchlorination conditions. Environ Sci Technol 2015;49:7348–55. CrossRefexternal icon
  7. Shields JM, Hill VR, Arrowood MJ, Beach MJ. Inactivation of Cryptosporidium parvum under chlorinated recreational water conditions. J Water Health 2008;6:513–20. CrossRefexternal icon
  8. CDC. Stay safe in and around swimming pools. Atlanta, GA: US Department of Health and Human Services, CDC; 2011.
  9. Trust for Public Land. 2011 city park facts. San Francisco, CA; 2011. iconexternal icon

* At the CDC-recommended pH of 7.2–7.8, CDC recommends maintaining free available chlorine at a minimum of 3ppm in hot tubs/spas and 1 ppm in other aquatic venues or free available bromine at a minimum of 4 ppm in hot tubs/spas and 3 ppm in other aquatic venues.

Entrapment occurs when a body part (e.g., hair, limb, or buttocks) or something on the swimmer’s body (e.g., jewelry or bathing suit) becomes caught in the suction of the recirculation pump or in an underwater structure.

§ The regulatory module ultimately was not included within the MAHC because its content was intended as guidance for state and local environmental health aquatic inspection programs rather than as guidance on the design, construction, operation, maintenance, and management of public aquatics facilities.

Return to your place in the text BOX. Fourteen Model Aquatic Health Code modules
  • Contamination burden
  • Disinfection and water quality
  • Facility design and construction
  • Facility maintenance and operation
  • Fecal/vomit/blood contamination response
  • Hygiene facilities
  • Lifeguarding and bather supervision
  • Monitoring and testing
  • Operator training
  • Preface, user guide, and definitions
  • Recirculation systems and filtration
  • Regulatory
  • Risk management/safety
  • Ventilation and air quality


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