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Bottom-up NAICS industry primers written for both public-market and private investors. Leaf industries are researched from the ground up; every group, subsector, and sector above them reads as a contrast across the industries beneath it.

2122 industries · 24 sectors · NAICS 2022

Researched with AI assistance from official U.S. statistics and independent sources, with citations on every page. Figures are not individually verified against pinned evidence — primers marked Evidence-verified are. Industry research, not investment advice. Methodology.

IndustryNAICS 22131Utilities

Water Supply and Irrigation Systems (NAICS 22131): An Investor's Primer

U.S. NAICS industry (5-digit) primer for a general investing audience — relevant to both public-market and private investors. This is a rollup page. At this level the industry is effectively identical to its single child industry, NAICS 221310, where the full detail lives. Core statistics are drawn from official U.S. federal sources; company and market figures are approximate and dated to mid-2026.

1. Overview

NAICS 22131 (the North American Industry Classification System, the standard U.S. government scheme for grouping businesses) is the business of collecting, treating, and piping drinking water and irrigation water to homes, businesses, and farms. For an investor it is one of the most defensive corners of the economy: water demand barely moves with the business cycle, each utility is a local monopoly, and prices are set by government regulators to let owners earn a steady, pre-approved profit.

The opportunity is that America's water infrastructure is old and expensive to fix — the U.S. Environmental Protection Agency (EPA) estimates a ~$625 billion 20-year drinking-water investment need [5] — and regulated utilities earn a return on every dollar they invest to replace it. The sector is also consolidating, headlined by a roughly $40 billion merger of its two largest players announced in October 2025 [10].

Investors reach it two ways: publicly, via a short list of listed water utilities, and privately, via infrastructure funds, direct ownership of systems, and public-private partnerships. One fact frames both routes — most U.S. water systems are owned by cities and towns, not companies — which is exactly why so much of the industry is a target for private capital.

2. What's inside — why this level equals its one child

This NAICS industry (5-digit) contains a single national industry (6-digit): 221310 — Water Supply and Irrigation Systems. There is no other child. As a result NAICS 22131 is a pass-through: the group's definition, scope, economics, and statistics are identical to 221310's. Everything an investor needs — the ownership structure, the rate-base model, the company list, demand drivers, regulation, and risks — is covered in full in the child primer.

What it covers: establishments that operate water treatment plants and/or water supply systems — pumping stations, aqueducts, distribution mains, canals, and reservoirs — to deliver water for drinking, irrigation, or other uses [1].

What it excludes: sewage/wastewater treatment (NAICS 221320), steam and air-conditioning supply (221330), bottled water manufacturing (312112), and pipeline/plumbing construction.

For the full detail, read the child primer: NAICS 221310 — Water Supply and Irrigation Systems. The rest of this page gives only the level's own figures and a compressed summary.

3. Size — this level's ground-truth figures

Because this is a single-child level, the rollup statistics are the 221310 statistics. From official federal sources:

  • ~$16.28 billion in annual receipts (2022 Economic Census) [1]
  • 3,887 firms (2022 Economic Census) [1]
  • 4,554 establishments, 43,082 employees, and ~$3.31 billion in annual payroll (County Business Patterns, 2023) [2]
  • Concentration: the four largest firms make about 40% of receipts (CR4 = 39.9%); the top 8 make 49.2%, the top 20 61%, and the top 50 70.8% (2022 Economic Census) [1]. The standard concentration index — the Herfindahl-Hirschman Index (HHI) — was suppressed by the Census for this industry, so no single-number figure is available [1].

Undercount caveat — read this before trusting the size. These are business statistics, and they capture mainly the private and quasi-private slice of water. The large majority of U.S. water systems are owned by governments (cities, towns, districts) — roughly 84% of community water systems, serving about 87% of Americans — and municipal water departments largely fall outside business surveys [4]. So the ~$16.28 billion receipts figure is best read as the private-sector baseline, not the whole industry. The physical asset base (pipes, plants, reservoirs) is worth vastly more — the EPA's 20-year need alone is ~$625 billion [5], and broader trackers that fold in government operations run to ~$132.5 billion in annual revenue on a wider definition [11].

4. The investable universe

Value in the listed portion of this group concentrates in a short list of pure-play regulated water utilities, which together serve the ~13% of the market owned by investor-owned utilities (IOUs — water systems owned by private companies rather than governments). The largest are American Water Works (AWK), Essential Utilities (WTRG), American States Water (AWR), California Water Service (CWT), and SJW Group (SJW), trailed by smaller names such as Middlesex Water (MSEX), York Water (YORW), Artesian Resources (ARTNA), and Global Water Resources (GWRS). The defining deal is AWK's pending ~$20.24 billion acquisition of Essential (announced October 27, 2025), which would create a ~$40 billion investor-owned water platform serving about 19.5 million people across 17 states, expected to close around Q1 2027 [10].

The far larger private and government universe sits alongside them: municipal water departments (the ~84% majority), plus infrastructure funds and privately held water companies that buy and operate systems. That municipal majority is the pool private capital is working to consolidate. The full company table, figures, and deal detail are in the child primer, Section 4.

5. How the money works

The economics are shared across the whole group because it is one industry. Regulated water utilities earn on a rate base × allowed return model: a state regulator tallies the utility's invested capital (pipes, plants, meters, reservoirs) minus depreciation to get the rate base, then sets customer rates so the utility recovers operating costs and depreciation plus a set profit percentage on that base — the allowed return on equity (ROE), recently around 9.5%–10.3% [13]. So capital spending is the growth story: every dollar invested (and allowed into the base) enlarges what the utility earns a return on. Water is exceptionally capital-intensive — utilities routinely invest more per year than they earn — and returns are dented by regulatory lag (the delay between spending and the rate increase that recovers it), which states soften via decoupling and infrastructure surcharges [11]. Because this level is a single child, there is no internal divergence between sub-industries to reconcile; see the child primer, Section 5.

6. Demand drivers

Growth is not about selling more water — usage is flat to falling — but about replacing and upgrading aging systems, which regulators let utilities earn a return on. The three big mandates:

  • Aging pipes: U.S. drinking water scored a C- on the American Society of Civil Engineers' 2025 Infrastructure Report Card; the EPA's 2023 assessment puts 20-year needs at ~$625 billion [5][8].
  • Lead service line replacement: an estimated 9+ million lead pipes remain; the EPA's Lead and Copper Rule Improvements (October 2024) require replacing essentially all of them within 10 years [6].
  • PFAS ("forever chemicals"): in April 2024 the EPA set the first national drinking-water limits on PFAS (per- and polyfluoroalkyl substances, a family of long-lasting industrial chemicals), with cost estimates ranging from ~$1.5 billion/year (EPA) to tens of billions (the American Water Works Association, AWWA) [7][9]. A May 2026 EPA proposal would roll back some limits and push deadlines toward 2031 — a moving target, but the direction is big mandated spending [7].

Each mandate is double-edged: it forces spending, but that spending grows the rate base utilities earn on.

7. Regulation

Two separate referees, which don't move in lockstep: state Public Utility Commissions (PUCs) set the economics (rates, allowed ROE, cost recovery) for investor-owned utilities [11][13]; the EPA under the Safe Drinking Water Act sets quality standards (maximum allowed levels of lead, PFAS, and other contaminants) for all systems, public or private [4][7]. The gap between them — quality rules can force sudden spending, but the money arrives only after a rate case — is the structural source of regulatory lag.

8. Consolidation

The long-term thesis is that thousands of small, cash-strapped municipal systems sell to better-capitalized buyers — listed utilities and, increasingly, private infrastructure funds. The accelerant is Fair Market Value (FMV) laws, adopted in about 13 states as of 2024, which let an acquirer put a municipal system's higher appraised value (rather than depreciated book value) into rate base — making deals more profitable and giving cities a reason to sell [14]. American Water closed 13 acquisitions in 2024 and guides to 15–25 deals a year [10]; layered on the AWK–Essential merger, consolidation is the clearest secular trend in the sector.

9. Risks

  • Regulatory and affordability risk: profit depends entirely on regulators, who can grant a lower ROE or deny a rate increase — especially as bills rise and investor-owned systems already charge meaningfully more than public ones [14].
  • Interest-rate sensitivity: the industry is capital-heavy and debt-financed; the listed names trade as "bond proxies" (income holdings whose prices tend to fall when rates rise) .
  • Compliance and contamination risk: PFAS and lead spending is recoverable eventually, but utilities face remediation, litigation, and the risk regulators disallow some spending [7][9].
  • Integration/execution risk: big deals need multi-state approvals and years of integration [10].
  • Weather/demand volatility: where revenue is not decoupled, a wet, cool year can dent it [11].

10. How to invest and the outlook

Two ways in. Public markets: own the listed water utilities — classic defensive, income holdings with dividend yields roughly 2.3%–4.3%, several of them long-run dividend growers, but trading at a premium price-to-earnings (P/E) multiple (many around 24–26x) that you pay for monopoly protection and visible rate-base growth [13]. Private markets: infrastructure and water-focused funds, direct ownership and operation of systems, and public-private partnerships — same rate-base return engine, often augmented by rolling up small systems.

Because this level is a pure pass-through, there is no "attractive sub-industry vs. at-risk sub-industry" split to make within it — the whole group rises and falls with the single 221310 industry. The near-term drivers to watch are the same ones listed there: (1) rate-base growth funded by the lead/PFAS/pipe-replacement capital cycle [5][6][7]; (2) municipal consolidation accelerated by FMV laws [14]; (3) the AWK–Essential merger closing (~Q1 2027) [10]; and (4) PFAS rule revisions and state PUC ROE decisions, which set how much of the spending actually earns a return [7][13].

Bottom line. Water is a slow, steady, regulation-driven industry — limited competition, predictable demand, and a decades-long government-mandated spending cycle that converts into rate-base growth — reachable through both public shares and private ownership. At the NAICS 22131 level it is simply its one child industry, 221310. For the complete analysis, read the child primer.

Sources

  1. U.S. Census Bureau — 2022 Economic Census, NAICS 221310 (receipts, firm counts, and CR4/CR8/CR20/CR50 concentration ratios; HHI suppressed). https://www.census.gov/programs-surveys/economic-census.html
  2. U.S. Census Bureau — County Business Patterns 2023, NAICS 221310 (establishments, employees, annual payroll). https://www.census.gov/programs-surveys/cbp.html
  3. U.S. Small Business Administration — Table of Small Business Size Standards (effective 2023); $41.0M average annual receipts for NAICS 221310. https://www.sba.gov/document/support-table-size-standards
  4. U.S. Environmental Protection Agency — Safe Drinking Water Information System (SDWIS) and drinking-water program data (public/community water system counts; population served; ownership split). https://www.epa.gov/ground-water-and-drinking-water
  5. U.S. Environmental Protection Agency — 7th Drinking Water Infrastructure Needs Survey and Assessment (2023); ~$625B 20-year need. https://www.epa.gov/dwsrf
  6. U.S. Environmental Protection Agency — Lead and Copper Rule Improvements (LCRI), October 2024. https://www.epa.gov/ground-water-and-drinking-water/lead-and-copper-rule
  7. U.S. Environmental Protection Agency — PFAS National Primary Drinking Water Regulation (April 2024) and subsequent 2026 revision proposal. https://www.epa.gov/sdwa/and-polyfluoroalkyl-substances-pfas
  8. American Society of Civil Engineers — 2025 Report Card for America's Infrastructure: Drinking Water (grade C-). https://infrastructurereportcard.org
  9. American Water Works Association (AWWA) — PFAS regulatory cost analyses. https://www.awwa.org
  10. American Water Works Company, Inc. & Essential Utilities, Inc. — merger announcement, October 27, 2025 (deal terms, pro forma scale, capital plans, acquisitions); via PR Newswire. https://www.prnewswire.com
  11. IBISWorld — Water Supply and Irrigation Systems in the US (NAICS 22131, broader definition), 2026 (industry revenue, decoupling/surcharge context). https://www.ibisworld.com
  12. National Association of Water Companies (NAWC) — fair-market-value legislation tracker (~13 states as of 2024). https://nawc.org
  13. Company filings and market data (approximate, mid-2026): market capitalizations, revenue, dividend yields, P/E multiples, and allowed-ROE / rate-case benchmarks for AWK, WTRG, AWR, CWT, SJW, MSEX, YORW, ARTNA, GWRS.
  14. Consumer-advocacy analysis of investor-owned vs. public water rates (~60–70% higher on average), as summarized in industry research, 2024.

Note: sources [12]–[14] here correspond to the fair-market-value, market-data, and rate-comparison sources cited as [14], [13], and [14] in the child primer.

Ground-truth note: core NAICS 22131 / 221310 statistics (receipts, firm/establishment counts, employment, payroll, concentration ratios) are taken from official U.S. Census Bureau data. Federal business statistics undercount the industry because the large majority of U.S. water systems are municipally/government-owned and fall outside private-business surveys — the single most important structural fact about this sector. Because NAICS 22131 has exactly one child industry (221310), the two levels are statistically and economically identical; this page summarizes and points to the child primer for full detail.