Can Tennessee carve out an exception from its drinking-water regulations so that water softeners installed at apartment buildings and large multifamily complexes are not treated as regulated 'treatment facilities'?

Subject

Installation of Water Softening Systems at Large Multifamily Housing Facilities and Apartment Complexes

Plain-English summary

A "point-of-entry" water softener installed where water comes into a large apartment building can technically tip the building into the federal definition of a regulated public water system. That brings monitoring and reporting obligations that no apartment owner wants for what is essentially an aesthetic upgrade (softer water for residents' showers and dishwashers). A Tennessee legislator asked whether the state can amend its Safe Drinking Water Act to declare that point-of-entry softeners at large multifamily buildings are not "treatment facilities," without losing federal primacy.

The AG concludes the answer is probably yes. The federal Safe Drinking Water Act gives states primary enforcement responsibility ("primacy") and only requires state rules to be "no less stringent" than federal ones. EPA guidance has been inconsistent on what counts as a "treatment facility," and the agency's most recent guidance (WSG 217, issued in 2022) has narrowed the concept. Several states with primacy (Florida, Oregon, Massachusetts) already exempt aesthetic-only treatment, and none of them has lost primacy. The opinion recommends Tennessee track one of those existing regimes if it wants to legislate.

What this means for you

For apartment owners and large multifamily property managers

If the legislature passes a softener exemption (modeled on Florida or Massachusetts), you would be able to install a point-of-entry softener for hard-water relief without inheriting the regulatory load of a "public water system" (sampling, reporting, certified operator, etc.). Until that bill passes, the safer course is to contact the Tennessee Department of Environment and Conservation before installing any whole-building softener that would tip you into PWS classification. The Massachusetts model also shows a hybrid path: limited regulatory obligations (notice, maintenance, monitoring) instead of full PWS oversight.

For water softener installers and HVAC contractors

Watch for legislation that creates a defined safe harbor. Tennessee has authority to follow the Florida or Massachusetts model. Until then, do not assume residential softener norms scale up; advise commercial clients about the federal definition of a public water system (15 service connections OR 25 individuals served regularly).

For state legislators considering the bill

The AG endorses the approach but flags two cautions. First, do not draft a wholesale exemption with no safeguards. Florida conditions its exemption on the treatment "not adversely affect[ing]" compliance with drinking water standards. Massachusetts imposes "minimum requirements" (notice to the state DEP and the supplying utility, maintenance responsibility, water-quality monitoring, wastewater-discharge compliance). Tennessee will want similar guardrails. Second, primacy depends on rules being "no less stringent" than federal. The federal floor is set by EPA's WSG 217 (2022), which narrowed but did not eliminate the "treatment facility" concept. Track the federal standard.

For TDEC and Tennessee water regulators

This opinion does not change current law. It frames a permissible legislative path. If the bill comes, TDEC will need rules implementing whatever safe harbor the legislature creates and a process for tracking installations and any monitoring conditions.

For tenants in multifamily buildings

Your building's water quality is governed both by what comes in from the public utility and by anything the building does with it. If the legislature creates an exemption with notice and maintenance conditions (as Massachusetts does), those conditions are what protect tenants. Ask your landlord whether a softener has been installed and what testing is being done.

Common questions

What is hard water and why does it need treatment?

Hard water is water with raised calcium and magnesium. It causes scale buildup, soap-curd, and reduced detergent effectiveness. EPA does not regulate calcium and magnesium because they are not health-threatening, but residents and property managers often want softening for aesthetic and equipment-protection reasons.

What is the difference between a point-of-entry and a point-of-use softener?

A point-of-entry device treats water as it enters the building. A point-of-use device treats water at a single fixture, like a kitchen sink. Tennessee regulations define both terms in Tenn. Comp. R. & Regs. 0400-45-01-.04.

What is a "public water system" under federal law?

A system that has at least 15 service connections OR regularly serves at least 25 people. 42 U.S.C. § 300f(4); 40 C.F.R. § 141.2. A large apartment building can meet either threshold.

What is "primacy"?

Primary enforcement responsibility under the federal Safe Drinking Water Act. States with primacy (currently 55 of 57 states and territories; Wyoming and DC are the exceptions) administer the SDWA in lieu of EPA. To keep primacy, a state's rules must be at least as stringent as federal rules. 42 U.S.C. § 300g-2.

Has EPA settled what counts as a "treatment facility"?

No. Earlier guidance (WSG 8A, WSG H26) read "treatment facility" broadly and treated point-of-entry devices as regulated facilities. WSG 217, issued in 2022, superseded that guidance and adopted a narrower view, at least for point-of-use devices. WSG 217 did not directly resolve the point-of-entry softener question for non-regulated contaminants.

What have other states done?

Florida (Fla. Admin. Code r. 62-550.102) excludes treatment facilities that are not necessary to comply with drinking water standards. Oregon (Or. Admin. R. 333-061-0010) excludes systems that consist only of distribution and storage facilities and that do not include source or treatment facilities installed for compliance. Massachusetts (310 Mass. Code Regs. 22.23(6)) creates a hybrid: aesthetic-only point-of-entry installations bypass full PWS regulation if they meet specified minimum requirements (notice, maintenance, monitoring, discharge compliance).

Has any of those states lost primacy?

No. According to EPA's own webpage, primacy is held by every state and territory except Wyoming and DC.

Will the AG's opinion bind the courts?

No. AG opinions are persuasive only. But this is a legislative-design opinion, not litigation, so the practical question is whether the General Assembly chooses to legislate.

Background and statutory framework

The federal Safe Drinking Water Act, enacted in 1974, sets uniform quality standards for public water systems. It is structured as cooperative federalism: EPA sets national primary drinking water regulations (42 U.S.C. § 300g-1) and states with primacy enforce them (§ 300g-2).

A "public water system" under 42 U.S.C. § 300f(4) is "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." A system is excluded from substantive SDWA regulation if it (1) consists only of distribution and storage facilities, (2) does not have any collection or treatment facilities, (3) obtains all of its water from another regulated PWS but is not owned or operated by that PWS, (4) does not sell water, and (5) is not an interstate carrier. 42 U.S.C. § 300g.

Tennessee's parallel statute, the Tennessee Safe Drinking Water Act of 1983 (§§ 68-221-701 to 68-221-720), tracks the federal definitions closely. Tenn. Code Ann. § 68-221-703(19); Tenn. Comp. R. & Regs. 0400-45-01-.03.

EPA guidance on what counts as a "treatment facility" has shifted. WSG 8A and WSG H26 read the term broadly: "if a building owner . . . installed a point of entry or point of use device, the device would be considered a 'treatment facility.'" WSG H26. WSG 217 (2022) superseded that guidance for point-of-use devices, holding that a point-of-use device "does provide treatment" but "is not a treatment facility." WSG 217 did not directly address point-of-entry units for unregulated contaminants like hardness.

Many states have drawn their own conclusions on what "treatment" means. The Association of State Drinking Water Administrators (ASDWA) found in its 2019 report that approximately 75% of state regulators surveyed in 2018 said softening did not trigger regulation as a consecutive public water system. ASDWA suggested that a more practical definition of treatment would be one that involves "technology that results in an adverse change in some regulated water parameter."

Three primacy states have adopted the practical definition by rule:

• Florida: "the phrase 'treatment facilities' shall exclude treatment facilities that are not necessary to achieve, and will not adversely affect, compliance with applicable drinking water standards and requirements." Fla. Admin. Code r. 62-550.102.
• Oregon: state rules do not apply to a PWS that consists "only of distribution and storage facilities, and does not include any source facilities or treatment facilities installed to comply with [maximum contaminant levels or treatment techniques]." Or. Admin. R. 333-061-0010.
• Massachusetts: 310 Mass. Code Regs. 22.23(6) treats aesthetic-only point-of-entry installations as consecutive PWSs but waives full monitoring/reporting if minimum requirements are met (notice to MassDEP and supplying utility, maintenance responsibility, monitoring per local direction, discharge compliance).

None of these states has lost primacy because of its approach.

The AG concludes that Tennessee can likely follow this path. The opinion recommends "closely track[ing] one of those existing regimes" rather than drafting from scratch.

Citations

• 42 U.S.C. §§ 300f(1), 300f(4), 300g, 300g-1, 300g-2 (Safe Drinking Water Act)
• 40 C.F.R. § 141.2
• Tenn. Code Ann. §§ 68-221-701 to 68-221-720 (Tennessee Safe Drinking Water Act)
• Tenn. Code Ann. § 68-221-703(19) (Tennessee PWS definition)
• Tenn. Comp. R. & Regs. 0400-45-01-.03 (Tennessee PWS exemptions)
• Tenn. Comp. R. & Regs. 0400-45-01-.04 (point-of-entry/point-of-use definitions)
• Fla. Admin. Code r. 62-550.102
• Or. Admin. R. 333-061-0010
• 310 Mass. Code Regs. 22.23(6)
• Grinnell v. EPA, 736 F. Supp. 3d 114 (N.D.N.Y. 2024)
• In re Flint Water Cases, 482 F. Supp. 3d 601 (E.D. Mich. 2020)
• United States v. King, 660 F.3d 1071 (9th Cir. 2011)
• Manufactured Hous. Inst. v. EPA, 467 F.3d 391 (4th Cir. 2006)
• Tenn. Att'y Gen. Op. 05-128 (Aug. 22, 2005)

Source

• Landing page: https://www.tn.gov/attorneygeneral/opinions.html
• Original PDF: https://www.tn.gov/content/dam/tn/attorneygeneral/documents/ops/2025/op25-010.pdf

Original opinion text

STATE OF TENNESSEE
OFFICE OF THE ATTORNEY GENERAL
May 7, 2025
Opinion No. 25-010

Installation of Water Softening Systems at Large Multifamily Housing Facilities and Apartment Complexes

Question
The Environmental Protection Agency regulates public water systems through the federal Safe Drinking Water Act which focuses on ensuring public water systems meet standards for contaminants and implement treatment techniques to achieve this goal. Without creating a conflict with federal standards, can Tennessee amend its state Safe Drinking Water Act to provide that a point-of-entry water softening system at a large multifamily housing facility or apartment complex is not a "treatment facility"?

Opinion
Probably. No judicial decision or agency guidance cleanly resolves this issue. But the best reading of the relevant statutory and regulatory authority suggests such legislation would be permissible, and there is broad support among States that softening does not trigger regulation as a consecutive water system. Some States with primacy authority have already adopted regulations that offer a pathway for building owners to use softening systems without incurring the normal regulatory burdens associated with public water systems.

ANALYSIS

The federal Safe Drinking Water Act ("the SDWA") "was passed in 1974 to establish uniform quality standards for the . . . public water systems in the United States." Grinnell v. EPA, 736 F. Supp. 3d 114, 119 (N.D.N.Y. 2024). Its statutory framework is one of "cooperative federalism," In re Flint Water Cases, 482 F. Supp. 3d 601, 622 (E.D. Mich. 2020), as it establishes "a federally mandated, state-administered regulatory scheme for the protection of drinking water." United States v. King, 660 F.3d 1071, 1077 (9th Cir. 2011). Although the SDWA tasks the EPA with promulgating national primary drinking water regulations, 42 U.S.C. § 300g-1, it also allows for States to exercise primary enforcement responsibility. This responsibility is commonly known as "primacy," and it can be delegated to States when they adopt requirements that are no less stringent than what is federally required. 42 U.S.C. § 300g-2. Tennessee, like most jurisdictions, has primacy.

At the outset, we emphasize that not every water contaminant is subject to substantive SDWA regulation. Nor is every water system. As to the former, the EPA's promulgation of primary drinking water regulations pertains to contaminants that the EPA Administrator has judged "may have any adverse effect on the health of persons." 42 U.S.C. § 300f(1). And as to the latter, only certain "public water systems" are subject to substantive SDWA regulation.

The SDWA's definition of a public water system is partially guided by considerations of a system's size and service population. 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." 42 U.S.C. § 300f(4). And the definition includes "any collection, treatment, storage, and distribution facilities under control of the operator of such system and used primarily in connection with such system." Id.; see also 40 C.F.R. § 141.2. But despite the breadth of the federal definition, a public water system is ultimately excluded from substantive SDWA regulation if it "consists only of distribution and storage facilities (and does not have any collection and treatment facilities)," "obtains all of its water from, but is not owned or operated by, a public water system to which such regulations apply," "does not sell water to any person," and "is not a carrier which conveys passengers in interstate commerce." 42 U.S.C. § 300g. Of note, the State Act's definition of a public water system closely hews to the federal standard, see Tenn. Code Ann. § 68-221-703(19), and Tennessee has implemented the same coverage exemption by way of regulation. See Tenn. Comp. R. & Regs. 0400-45-01-.03.

The question presented is whether Tennessee could permissibly amend the State Act to exclude water softening systems at large multifamily housing facilities or apartment complexes from its regulatory scope.

That question implicates something of a legal gray area. The EPA itself has offered shifting guidance as to what constitutes a "treatment facility." Prior Water Supply Guidance ("WSG") H26, for instance, stated that, "[g]enerally, the term 'treatment facilities' should be interpreted broadly." And under prior WSG H26, "if a building owner . . . installed a point of entry or point of use device, the device would be considered a 'treatment facility.'" Recent EPA guidance, however, has promoted a narrower understanding. Under WSG 217, which issued in 2022, the EPA specifically addressed the status of point-of-use devices. Although the EPA reasoned that a point-of-use device "does provide treatment," it concluded a point-of-use device "is not a treatment facility." But WSG 217 did not directly grapple with the question of whether point-of-entry units aimed at addressing non-regulated water contaminants should be considered treatment facilities. Indeed, there is no federal standard for "hard water," as the constituents generally contributing to hardness—calcium and magnesium ions—are not considered toxic by the federal government.

With no judicial resolution or clear and persuasive on-point guidance, many States have drawn their own conclusions on the meaning of "treatment." According to a report from the Association of State Drinking Water Administrators ("the ASDWA"), two surveys of thirty primacy agencies in the 2010s revealed a "great diversity of opinion among states on exactly what constitutes 'treatment.'" According to a 2018 survey, approximately 75% of respondents considering the issue answered that softening was a process that did not trigger regulation as a consecutive public water system. The ASDWA has suggested that a more practical definition of treatment would be one that involves "technology that results in an adverse change in some regulated water parameter."

Some States have expressly enacted regulations that appear to implement the "more practical" definition touted by the ASDWA. Florida, for instance, specifically provides that "the phrase 'treatment facilities' shall exclude treatment facilities that are not necessary to achieve, and will not adversely affect, compliance with applicable drinking water standards and requirements." Fla. Admin. Code Ann. r. 62-550.102. Similarly, Oregon provides that its State drinking water rules do not apply to a public water system that, among other things, consists "only of distribution and storage facilities, and does not include any source facilities or treatment facilities installed to comply with [maximum contaminant levels or treatment techniques]." Or. Admin. R. 333-061-0010. And Massachusetts also appears to generally countenance non-regulation of buildings that install water softening systems, at least insofar as the full suite of monitoring and reporting requirements for public water systems may be at issue. 310 Mass. Code Regs. 22.23(6).

These States have sensibly focused on whether a system is used to achieve compliance regarding a regulated contaminant. Moreover, as far as we are aware, these States have not lost primacy because of their regulatory approaches.

With all the foregoing in mind—and considering that a water softening system is not used to address regulated water contaminants—specific legislative action to exclude such a system from the definition of a "treatment facility" would likely be permissible. As other jurisdictions that have allowed point-of-entry softening units in multifamily facilities have not lost primacy, the most prudent course for Tennessee legislation would be to closely track one of those existing regimes.

JONATHAN T. SKRMETTI
Attorney General and Reporter

J. MATTHEW RICE
Solicitor General

MATTHEW KERNODLE
Assistant Attorney General

Requested by:
The Honorable Clark Boyd
State Representative
Cordell Hull Building, Suite 528
425 Rep. John Lewis Way North
Nashville, Tennessee 37243