Where Our Data Comes From

Transparency is our foundation. Here's exactly where our data comes from and how we analyze it.

Monthly

Data Updates

Primary Data Sources

100%

Source Verification

Comprehensive Federal Data Sources

EPA Safe Drinking Water Information System (SDWIS)

The foundation of our water quality data

EPA's SDWIS database contains information on all public water systems in the United States—the most comprehensive federal water quality repository.

Basic system information for 150,000+ public water systems including name, location, and population served
Violation tracking for health-based violations, monitoring failures, and treatment violations
Contaminant data for 90+ regulated contaminants under the Safe Drinking Water Act

EPA Water Quality Portal (WQP)

297 million water quality records from 400+ agencies

The Water Quality Portal integrates data from USGS, EPA, and over 400 state, federal, tribal, and local agencies—the most comprehensive source of discrete water quality data in the United States.

Consumer Confidence Reports (CCRs)

Annual water quality reports from local utilities

Every community water system serving 25+ people must deliver an annual Consumer Confidence Report by July 1st, containing the most recent local water quality testing data.

Source water information including lakes, rivers, aquifers, or groundwater
Detected contaminant levels with actual testing results for your water system
Compliance status showing whether federal and state requirements were met

State and Local Water Quality Databases

California CEDEN

California operates one of the most comprehensive state monitoring programs, providing additional detail on streams, lakes, rivers, and coastal waters beyond federal requirements.

State Monitoring

State programs often have stricter standards than federal requirements:

• California: Stricter chromium limits
• Texas: TCEQ additional monitoring
• Enhanced programs nationwide

Municipal Data

Many cities conduct additional testing beyond EPA requirements. We access municipal databases for the most complete local water quality picture.

Filter Certification Databases

NSF International writes many of the drinking water treatment standards, and ANSI approves them — which is why they are named “NSF/ANSI 42”, “NSF/ANSI 53” and so on. But NSF is not the only organization that certifies products against those standards. Several accredited certification bodies do, and each publishes its own directory of the products it has certified.

A filter listed by WQA, IAPMO R&T, UL Solutions or CSA Group is certified to the same standard, tested to the same thresholds, as one listed by NSF. It simply appears in a different directory. Searching only NSF’s database and finding no match does not mean a product is uncertified.

CSA Group

Certifies drinking water treatment products to the NSF/ANSI standards and publishes them in its own product listing directory.

csagroup.org product listing →

IAPMO R&T

Certifies water treatment products to the NSF/ANSI standards and lists them in the IAPMO R&T Product Listing Directory.

pld.iapmo.org →

NSF International

Certifies drinking water treatment units to the NSF/ANSI standards and lists the products it has certified in its DWTU directory.

info.nsf.org/certified/dwtu →

UL Solutions

Certifies water treatment products to the NSF/ANSI standards and publishes its listings through the Product iQ directory.

productiq.ulprospector.com →

WQA Gold Seal

The Water Quality Association's certification program. Certifies to the NSF/ANSI standards, with annual plant inspections and material safety review, and lists products in its Gold Seal directory.

find.wqa.org →

What we currently index

Our certification data is built from the NSF International, WQA Gold Seal and IAPMO R&T directories. We do not yet ingest UL Solutions or CSA Group listings, so a product certified only by one of those two may not appear in our lookup tool. We are working on adding them. If a filter you own is certified and missing from our data, tell us and we will correct it.

Data Quality and Verification

Federal Data Reliability

Our federal sources represent the most reliable water quality information available:

• SDWIS compliance legally required under Safe Drinking Water Act
• Quality control through EPA validation protocols
• Regular updates quarterly SDWIS, annual CCRs

Certification Verification

All filter certification data from accredited testing organizations:

• ANAB accreditation NSF and WQA accredited by ANSI
• Independent testing $100k+ per product costs
• Ongoing verification regular retesting and inspections

Our Processing & Validation

We implement multiple data quality controls:

• Source verification traced to original sources
• Consistency checks cross-validation between sources
• Update monitoring automated new data detection
• Error detection algorithms flag anomalies

Addressing Current Market Failures

Comprehensive Coverage vs. Selective Data

Unlike databases that cherry-pick alarming data points, we provide complete water quality pictures using established EPA standards. We cross-reference with actual EPA maximum contaminant levels (MCLs) and state standards to provide accurate context.

Real-Time Updates vs. Outdated Information

While some databases rely on 2019 data, we continuously update with the most recent CCRs and government data releases—ensuring recommendations based on current conditions, not outdated information.

Actionable Solutions vs. Fear-Based Reporting

Rather than simply listing potential contaminants, we connect specific water quality issues to certified filter solutions—providing the practical guidance consumers need to make informed decisions.

Every Data Point is Traceable

Every data point in our system is traceable to its authoritative source, ensuring transparency, accuracy, and reliability in our water quality assessments and filter recommendations.