I. The Statutory Definition

The Safe Drinking Water Act of 1974, as amended and codified at 42 U.S.C. § 300f et seq., is the principal federal statute governing the safety of water provided to the American public for consumption. Its regulatory architecture begins with a definition.¹

Section 300f(4)(A) provides: “The term ‘public water system’ means a system for the provision to the public of water for human consumption through pipes or other constructed conveyances, if such system has at least fifteen service connections or regularly serves at least twenty-five individuals daily at least sixty days out of the year.”

This definition establishes four elements. First, provision to the public. Second, water for human consumption. Third, delivery through pipes or other constructed conveyances. Fourth, a service threshold—either fifteen connections or twenty-five daily users for sixty days.

The statute does not specify that the water must be provided in a glass. It does not require that the consumer hold the water in a cup. It does not stipulate that the consumption must be voluntary, informed, or even noticed by the person consuming it. It requires only that the system provide water for human consumption through constructed conveyances to a sufficient number of people. A public swimming pool satisfies every element.

II. The Constructed Conveyances

A public swimming pool is not a pond. It is not a natural body of water fed by springs and drained by gravity. It is a precision-engineered water distribution system composed entirely of constructed conveyances.

The typical public pool operates through a closed-loop hydraulic system consisting of main drains, skimmers, suction lines, circulation pumps rated at 50 to 150 gallons per minute, sand or diatomaceous earth filters, chemical feed systems, return lines, and wall or floor inlets that distribute the treated water back into the basin.² The water in a public pool passes through this conveyance system every six to eight hours—a turnover rate that most municipal water utilities would consider ambitious. The Pool & Hot Tub Alliance, formerly the Association of Pool and Spa Professionals, reports that the plumbing system of a standard commercial pool contains between 200 and 800 linear feet of PVC piping, the same Schedule 40 pipe that carries drinking water from the utility main to the kitchen faucet.

The EPA’s own regulations define “constructed conveyance” nowhere in 40 CFR Part 141. The agency has never drawn a line between a pipe that carries water to a showerhead and a pipe that carries water to a pool return jet. Both are pipes. Both carry treated water. Both terminate at a point where the water contacts a human body. The regulatory distinction between them is, in hydraulic terms, a fiction.

III. The Service Threshold

The Safe Drinking Water Act’s service threshold is modest by design. Congress set the bar at twenty-five individuals daily for sixty days to capture small systems—rural water cooperatives, mobile home parks, campgrounds, highway rest areas. The threshold was not intended to be difficult to reach. It was intended to be inclusive.

The average public swimming pool in the United States serves between 100 and 300 swimmers per day during the operating season, which typically runs from late May through early September—approximately 100 days.³ Major municipal pools serve over 1,000 swimmers per day. The CDC’s Model Aquatic Health Code estimates that more than 309,000 public and semi-public swimming pools operate in the United States, alongside approximately 5 million residential pools.⁴ The Sports and Fitness Industry Association reported in 2023 that approximately 91.3 million Americans swam at least once during the prior year, making swimming the fourth most popular recreational activity in the country.

These facilities do not approach the twenty-five-person threshold. They exceed it by orders of magnitude, continuously, for the entire operating season. A municipal pool that opens on Memorial Day and closes on Labor Day operates for approximately 99 days—39 days more than the sixty-day statutory minimum. A YMCA pool that operates year-round exceeds the threshold by 305 days. A hotel pool that serves guests from March through November exceeds it by approximately 215 days. Not one of them is classified as a public water system.

IV. The Consumption Evidence

The statutory definition requires water “for human consumption.” The EPA interprets this phrase broadly. Under 40 CFR § 141.2, “human consumption” encompasses not only drinking but also bathing, showering, cooking, dishwashing, and maintaining oral hygiene—any activity in which water contacts the human body or enters the human digestive system.⁵ Swimming involves both.

The question of whether swimmers consume pool water is not theoretical. It has been measured, quantified, and published in the peer-reviewed literature with the precision of a pharmaceutical dosing study.

In 2006, Alfred Dufour and colleagues at the EPA’s own National Exposure Research Laboratory published the results of a controlled water ingestion study in the Journal of Water and Health, a World Health Organization publication.⁶ Using cyanuric acid as a tracer compound, the researchers measured the volume of pool water involuntarily swallowed by swimmers during 45-minute swimming sessions. Adults ingested a median of 37 milliliters per session. Children aged 7 to 17 ingested a median of 45 milliliters. Children under 7—the demographic most likely to be found in a public wading pool—ingested substantially more, with some individuals consuming over 150 milliliters in a single session.

For context, 37 milliliters is approximately 2.5 tablespoons. It is more water than is contained in a standard medical dosing cup. It is a volume that, if it contained a regulated contaminant at the maximum contaminant level, would deliver a quantifiable dose to the consumer. The EPA’s own risk assessment models for drinking water exposure assume a default daily ingestion rate of 2.2 liters per day for adults. A competitive swimmer training for two hours per day in a pool would add approximately 99 milliliters to that daily intake—a 4.5 percent increase in total water consumption from an entirely unmonitored source.

V. The Contaminant Profile

The Safe Drinking Water Act requires the EPA to establish National Primary Drinking Water Regulations for contaminants that may have adverse health effects and are known or substantially likely to occur in public water systems. The agency currently regulates over ninety contaminants across six categories: microorganisms, disinfectants, disinfection byproducts, inorganic chemicals, organic chemicals, and radionuclides.⁷

Public swimming pool water contains contaminants from every one of these categories.

Microorganisms: The CDC’s own surveillance data, published in the Morbidity and Mortality Weekly Report, documented 493 recreational water–associated disease outbreaks between 2000 and 2014, resulting in at least 27,219 cases of illness and eight deaths.⁸ Cryptosporidium, a chlorine-resistant protozoan parasite, was the leading cause, responsible for 58 percent of outbreaks associated with treated recreational water in the most recent reporting period. Pseudomonas aeruginosa, Legionella, and norovirus accounted for the majority of the remainder. Every one of these organisms appears on the EPA’s Contaminant Candidate List or is regulated under the Surface Water Treatment Rules.

Disinfectants: Public pools maintain free chlorine concentrations between 1.0 and 3.0 milligrams per liter, with some facilities operating at 5.0 mg/L or higher after superchlorination events.⁹ The EPA’s Maximum Residual Disinfectant Level for chlorine in drinking water is 4.0 mg/L, established under the Stage 1 Disinfectants and Disinfection Byproducts Rule at 40 CFR § 141.65. A pool operating at the upper end of its recommended range is running at 75 percent of the federal drinking water disinfectant limit. A pool that has just been shocked is exceeding it.

Inorganic chemicals: Cyanuric acid, the chlorine stabilizer used in virtually all outdoor pools, is present at concentrations of 30 to 100 mg/L. Copper sulfate, used as an algaecide, introduces copper at levels that can exceed the EPA’s action level of 1.3 mg/L. The pH adjustment chemicals—sodium carbonate, muriatic acid, sodium bisulfate—leave residual ions in the water column at concentrations that no drinking water utility would tolerate without monitoring.

VI. The Disinfection Byproduct Paradox

The most consequential regulatory gap is not the contaminants that enter the pool water. It is the contaminants that the pool water creates.

When chlorine reacts with organic matter in water, it produces a family of compounds known as disinfection byproducts. The most significant are trihalomethanes—chloroform, bromodichloromethane, dibromochloromethane, and bromoform—and haloacetic acids. The EPA classified these compounds as probable human carcinogens and, after decades of rulemaking, established a Maximum Contaminant Level of 80 micrograms per liter for total trihalomethanes under the Stage 2 Disinfectants and Disinfection Byproducts Rule, codified at 40 CFR § 141.64.¹⁰

In a municipal water system, the organic precursor material consists primarily of naturally occurring humic and fulvic acids from the source watershed. In a swimming pool, the organic precursor material consists of the swimmers themselves. Human skin, hair, sweat, urine, saliva, sunscreen, cosmetics, and fecal matter—euphemistically termed “bather load” in the pool industry literature—react with hypochlorous acid to produce disinfection byproducts at concentrations that dwarf those found in treated drinking water.

A 2002 study published in Occupational and Environmental Medicine by Chu and Nieuwenhuijsen measured trihalomethane concentrations in indoor swimming pools and found mean total THM levels ranging from 43.1 to 174.7 μg/L, with individual facilities exceeding 400 μg/L.¹¹ Aggazzotti and colleagues, publishing in Environmental Research, measured chloroform alone at concentrations of 36 to 524 μg/L in Italian indoor pools.¹² A comprehensive review by Richardson and colleagues in Environmental Health Perspectives documented over 100 disinfection byproducts in swimming pool water, including some that are not found in drinking water at all because the organic precursors in drinking water—leaves and soil—are fundamentally different from the organic precursors in pools—people.¹³

The paradox is structural. The EPA requires every municipal water system in the country to monitor trihalomethanes quarterly, report the results to the state primacy agency, and maintain running annual averages below 80 μg/L. A water utility that exceeds this level faces enforcement action, mandatory public notification, and potential civil penalties. A swimming pool in the same municipality, operating with THM concentrations two to five times the federal drinking water limit, in a basin into which 91 million Americans voluntarily lower their bodies and involuntarily open their mouths, is subject to no federal monitoring requirement at all.

VII. The Dual Exposure Pathway

The regulatory gap is compounded by the fact that swimming pool exposure operates through two pathways simultaneously, both of which the EPA considers relevant to human health risk assessment.

The first is ingestion, documented by Dufour and colleagues at 37 milliliters per session for adults. The second is inhalation. Volatile disinfection byproducts—chloroform, in particular—evaporate from the pool surface and concentrate in the breathing zone immediately above the water line, precisely where a swimmer’s face is located during front-crawl, breaststroke, and backstroke.

Lévesque and colleagues, publishing in Environmental Health Perspectives, measured the chloroform concentration in the breathing zone of swimmers in indoor pools at 72 to 562 μg/m³.¹⁴ The EPA’s own Integrated Risk Information System assigns chloroform an inhalation unit risk of 2.3 × 10&sup-5; per μg/m³ for lifetime cancer risk. The Agency for Toxic Substances and Disease Registry has established a chronic inhalation Minimal Risk Level for chloroform of 50 μg/m³. A swimmer inhaling at the surface of an indoor pool can be exposed to chloroform concentrations exceeding the ATSDR’s chronic MRL within a single lap.

The EPA’s drinking water regulations account for ingestion exposure only. Its ambient air quality standards do not cover indoor air. OSHA’s permissible exposure limits apply to workers, not recreational swimmers. No federal agency regulates the inhalation of volatile disinfection byproducts by the 91 million Americans who swim in chlorinated pools. The exposure pathway exists. The science documenting it exists. The regulatory authority to address it does not.

VIII. The Consumer Confidence Void

Under 40 CFR § 141.153, every community water system in the United States must deliver an annual Consumer Confidence Report to every person served by the system.¹⁵ The report must identify every regulated contaminant detected in the water, state the level detected, state the EPA’s maximum contaminant level for that substance, identify the likely source of contamination, and provide a plain-language health effects statement for any contaminant detected above the MCL.

This is the most transparent disclosure regime in American environmental law. It applies to the water that comes out of the tap at the concession stand next to the pool. It does not apply to the water in the pool.

No public swimming pool in the United States has ever issued a Consumer Confidence Report. No swimming pool has ever disclosed its trihalomethane concentration to its users. No swimming pool has ever identified the source of the organic contamination in its water—which is, of course, the users themselves. No swimmer in American history has received a notice stating: “Total trihalomethanes in this facility were measured at 247 μg/L in the most recent sampling period, exceeding the EPA’s Maximum Contaminant Level of 80 μg/L by a factor of 3.1. The likely source of contamination is you.”

The Consumer Confidence Report was created because Congress and the EPA determined that the public has a right to know what is in the water they consume. The public consumes pool water. The public does not know what is in it. The informational right exists. The information does not.

IX. The Operator Certification Gap

Under section 1419 of the Safe Drinking Water Act, 42 U.S.C. § 300g-8, the EPA requires every state to implement an operator certification program for public water systems. These programs establish minimum qualifications, examination requirements, and continuing education standards for the personnel responsible for treating and distributing the water that the public drinks.¹⁶

The EPA has established guidelines specifying that operators of community water systems must pass a validated examination covering water chemistry, microbiology, treatment processes, regulatory requirements, and distribution system management. The certification must be renewed periodically, and operators must complete continuing education hours to maintain their credentials. There are approximately 200,000 certified drinking water operators in the United States.

Pool operators are not subject to these requirements. The CDC’s Model Aquatic Health Code recommends that pool operators obtain a Certified Pool Operator or Aquatic Facility Operator credential, but these certifications are voluntary at the federal level and inconsistently mandated at the state level. The CDC’s own inspection data, published in 2016, found that 79.1 percent of public aquatic facilities inspected had at least one violation, and 12.1 percent had violations serious enough to warrant immediate closure—including improper disinfectant levels and absent safety equipment.¹⁷

The person who adds chlorine to the water supply at the municipal treatment plant holds a state-issued operator certification that requires examination, experience, and renewal. The person who adds chlorine to the water supply at the community pool may hold no certification at all. Both are adding the same chemical to water that the public will consume. One is regulated. The other is not.

X. The Sanitary Survey Exemption

Under 40 CFR § 142.16, the EPA requires states to conduct periodic sanitary surveys of every public water system within their jurisdiction. A sanitary survey is a comprehensive on-site review of the water system’s source, treatment, distribution, finished water quality, management and operations, operator compliance, data verification, and system security. Community water systems must undergo a sanitary survey at least every three years. Non-community systems must undergo one at least every five years.

The purpose of the sanitary survey is to verify that the system is capable of providing water that meets all applicable National Primary Drinking Water Regulations. The survey examines every component of the system from source to tap.

No sanitary survey has ever been conducted on a swimming pool under the Safe Drinking Water Act. The source water—which is municipal tap water, itself the product of a federally regulated public water system—enters the pool clean and compliant. It then sits in an open basin exposed to ultraviolet radiation, wind-borne debris, bird droppings, insect incursion, and the continuous input of organic matter from human bodies. It is recirculated through a treatment system that adds disinfectants and removes particulates. It emerges from the return jets as a water product that has been fundamentally altered in chemical composition from the source water that entered the fill line. At no point in this transformation does a federal sanitary survey examine the result.

The irony is precise. The EPA sanitary survey program exists because the agency determined that source-to-tap oversight is essential to protecting public health. The swimming pool is a system that takes federally inspected water, subjects it to chemical transformation and biological contamination, and delivers the altered product to the public for consumption—and no federal inspector examines any of it.

XI. The CDC’s Own Admission

The Centers for Disease Control and Prevention developed the Model Aquatic Health Code in 2014 precisely because no federal regulatory framework for recreational water exists. The MAHC is not a regulation. It is a voluntary guidance document—a suggested framework that states and localities may adopt, in whole or in part, or ignore entirely.¹⁸

The MAHC’s own introduction states: “There is no single federal agency with regulatory authority over public aquatic facilities.” This is the CDC acknowledging, in a published document, that the water in which 91 million Americans immerse themselves and from which they involuntarily drink is governed by no federal statute, no federal regulation, and no federal agency. The acknowledgment is refreshingly honest. It is also a description of the largest unregulated water distribution system in the country.

The MAHC recommends water quality standards. It recommends operator training. It recommends monitoring and reporting. It does not require any of them. The result is a patchwork of state and local codes that vary so widely that a pool operating legally in one jurisdiction would be shut down in another. Some states require daily water quality testing. Others require weekly testing. Others require no testing at all. The frequency, parameters, and reporting requirements are determined by the state health department, if one exists, and by the local health authority, if it has the funding and staff to conduct inspections.

The EPA regulates every community water system with fifteen or more service connections. It does not regulate a single swimming pool with fifteen hundred daily users. The gap is not one of oversight. It is one of classification. The swimming pool, by any functional analysis of the statutory definition, is a public water system. The EPA has simply decided that it is not.

XII. The Enforcement Asymmetry

Under 42 U.S.C. § 300g-3, the EPA may issue administrative orders and assess civil penalties of up to $25,000 per day of violation against any public water system that fails to comply with the National Primary Drinking Water Regulations. Under the 1996 amendments, the maximum penalty was increased to $55,000 per violation per day, adjusted for inflation. The agency has exercised this authority thousands of times.¹⁹

A community water system that serves 25 households and experiences a single day of trihalomethane exceedance at 85 μg/L—five micrograms above the MCL—faces public notification requirements, corrective action orders, and potential penalties. A community swimming pool that serves 500 swimmers per day at trihalomethane concentrations of 300 μg/L—nearly four times the MCL—faces no federal consequence of any kind. The system has no federal ID number. It files no monitoring reports. It is not entered in any EPA database. It does not exist in the federal regulatory universe.

This is not an oversight in enforcement. It is a categorical exclusion from the regulatory framework that Congress designed to protect the public from contaminated water. The exclusion has no textual basis in the statute. Section 300f(4)(A) does not exempt recreational water systems. It does not exempt water provided for immersion rather than ingestion. It does not exempt water that contacts the body through a basin rather than a faucet. The definition is functional: water for human consumption, through constructed conveyances, to twenty-five or more people. The swimming pool satisfies the definition. The EPA has chosen not to apply it.

XIII. Conclusion

The evidence is hydraulic, chemical, epidemiological, and statutory. Under 42 U.S.C. § 300f(4)(A), a “public water system” is a system for the provision to the public of water for human consumption through pipes or other constructed conveyances that regularly serves at least twenty-five individuals. Public swimming pools provide water. They use constructed conveyances. They serve hundreds or thousands of individuals daily. The water is consumed—involuntarily, continuously, and at rates that the EPA’s own researchers have measured and published.

The water contains regulated contaminants. It contains disinfection byproducts at concentrations that exceed the EPA’s own Maximum Contaminant Levels by factors of two to five. It is the source of documented disease outbreaks totaling tens of thousands of illnesses over the past two decades. It is treated by operators who may hold no certification recognized under the Safe Drinking Water Act and monitored by systems that file no reports with any federal agency.

The tap water fountain on the pool deck has a federal identification number, an approved sanitary survey, a certified operator, a quarterly monitoring schedule for over ninety contaminants, and an annual Consumer Confidence Report mailed to every customer. The eighty thousand gallons of trihalomethane-laden, Cryptosporidium-harboring, bather-load-enriched water six feet away has none of these things.

The Safe Drinking Water Act was written to regulate systems that provide water for human consumption through constructed conveyances. The swimming pool is such a system. The consumption is documented. The conveyances are constructed. The contaminants are measured. The health effects are published. The regulatory framework is in place. The only thing missing is the will to apply it to a system in which the consumers are wearing swimsuits instead of holding glasses.

The statute does not distinguish between the two. The EPA does.

Ergo.