Plumbing Listings

The plumbing listings on this directory cover licensed contractors, water treatment specialists, and plumbing service providers operating across the United States with documented experience in water filtration installation, maintenance, and system integration. Entries are organized to help property owners, facility managers, and building professionals locate practitioners matched to specific filtration technologies and project types. Understanding how entries are structured, what data is included, and where coverage gaps exist helps readers use the directory accurately rather than inferring completeness where none is claimed. For broader context on why this resource exists and how it fits into a larger reference framework, the plumbing-directory-purpose-and-scope page provides foundational detail.

How to read an entry

Each listing presents structured data fields in a consistent order. Readers should treat each field as an independent data point rather than reading an entry as a holistic endorsement. The standard field sequence is:

1. Business name — The registered trade name as it appears on state licensing records or EPA-recognized certification databases where applicable.
2. License type and number — Identifies the category of license held (e.g., master plumber, journeyman plumber, water treatment specialist). License class definitions follow state-level plumbing codes, which in most states are modeled on the Uniform Plumbing Code (UPC) published by the International Association of Plumbing and Mechanical Officials (IAPMO) or the International Plumbing Code (IPC) published by the International Code Council (ICC).
3. Service geography — Lists counties, metropolitan statistical areas (MSAs), or states where the provider actively accepts work. Geographic scope is self-reported by the listed entity.
4. Filtration specialties — Categorizes the types of filtration systems the provider installs or services. Categories map to system types described in the water-filtration-systems-overview reference, including point-of-entry whole-house systems, point-of-use water filters, reverse osmosis systems, UV disinfection units, and specialty contaminant-targeted systems such as PFAS filtration and lead filtration assemblies.
5. NSF/ANSI certification familiarity — Indicates whether the provider has documented experience installing equipment certified under NSF/ANSI standards, specifically NSF/ANSI 58 (reverse osmosis), NSF/ANSI 42 (aesthetic effects), or NSF/ANSI 53 (health effects).
6. Permit and inspection record — Where available, notes whether the provider operates in jurisdictions that require permit-pull documentation for filtration system installation. Permit requirements for water filtration work vary by state and municipality; the International Residential Code (IRC) Section P2902 governs backflow prevention requirements that trigger permit obligations in many jurisdictions.

Entries that lack a license number field have not completed verification (see Verification Status below) and are flagged with a pending indicator.

What listings include and exclude

Included:
- Licensed plumbing contractors with at least one filtration system specialty on record
- Water treatment dealers and installers who hold Water Quality Association (WQA) certification or equivalent credentialing
- Commercial plumbing firms with documented experience in water filtration for commercial plumbing applications
- Providers who service well-water systems, including those addressing iron filtration, arsenic filtration, and hydrogen sulfide filtration

Excluded:
- General plumbers with no documented filtration work, even if licensed
- Equipment retailers who do not offer installation services
- Providers operating exclusively outside the United States
- Individuals or firms with open disciplinary actions on a state licensing board at the time of entry review

The directory does not include manufacturer representatives, warranty-only service technicians, or DIY-focused consultants. The distinction between a licensed plumber and a water treatment specialist is substantive — the plumber-vs-water-treatment-specialist page outlines the jurisdictional and competency differences that affect which professional type is appropriate for a given project.

Verification status

Listings fall into three verification tiers:

• Verified — License number confirmed against the relevant state licensing board database; at least one filtration specialty confirmed through WQA, NSF, or equivalent third-party credentialing documentation.
• Pending — License number provided but not yet cross-checked against the state database. Filtration specialties are self-reported.
• Unverified — Entry submitted but no license number or third-party credential has been supplied. These entries are published with a clear unverified flag and must not be treated as endorsed listings.

Verification status is reviewed on a rolling cycle. State licensing board databases are the primary reference for plumbing license validation; the National Contractors License Service (NCLS) and IAPMO's verification portal serve as supplementary checks. EPA drinking water standards do not directly govern contractor licensing, but they establish the contaminant reduction benchmarks that certified equipment must meet — and by extension inform the relevance of a provider's equipment familiarity.

Coverage gaps

The directory does not claim national completeness. Coverage density reflects submission volume and verification throughput rather than the actual distribution of qualified providers across the United States. The following gaps are known:

• Rural and frontier counties — Providers serving populations below 2,500 in rural census-designated areas are underrepresented. Well-water filtration specialists in particular, who serve the roughly 43 million Americans on private wells (U.S. Geological Survey, Estimated Use of Water in the United States), appear at lower density than their actual market presence.
• Specialty contaminant categories — Providers focused narrowly on nitrate filtration systems or emergency water filtration are sparse in the directory relative to the number of affected communities identified in EPA Safe Drinking Water Act compliance reporting.
• New construction integration — Firms specializing in water filtration for new construction are a distinct subset; the directory currently holds fewer than 40 verified entries in this subcategory nationally.
• State-specific regulatory variation — Water filtration regulations by state vary significantly; providers in states with stricter licensing overlays (California, Massachusetts, and Washington maintain notable requirements) are listed at higher verification confidence than those in states without mandatory water treatment contractor licensing.

Gaps identified by readers or industry organizations can be reported through the contact page. Submissions undergo the same verification sequence described above before publication.