Our Methodology

Overview

Filter Tested operates in a Research-Backed Editorial Analysis mode. We do not operate a physical laboratory; instead, we conduct deep, structured research using publicly available technical documentation, independent laboratory test results, third-party certifications, and manufacturer specifications. Every product we cover is evaluated against the same transparent criteria so readers can make direct, meaningful comparisons.

Our methodology is designed to answer one question: Does this water filtration system deliver what it promises at a fair value?

Evidence Sources

Our evaluations draw from verified, authoritative sources:

• Manufacturer Specifications: Official product datasheets, user manuals, and technical documentation provided by the brand.
• NSF/ANSI Certifications: Publicly listed certification data from NSF International and the American National Standards Institute, including standards 42, 53, 401, P473, and 58.
• EPA Guidelines: Reference data from the U.S. Environmental Protection Agency on maximum contaminant levels (MCLs) and water quality standards.
• Independent Laboratory Reports: Published third-party test results from certified laboratories when publicly available.
• Verified User Feedback: Aggregated, thematically analyzed user reviews from multiple retail platforms to identify real-world performance patterns.

Evaluation Criteria

Each product is scored on a 100-point scale across five weighted dimensions:

1. Filtration Performance (30%)

We assess the system's ability to remove or reduce targeted contaminants. This includes evaluating published contaminant reduction percentages, flow rate (gallons per minute), filter lifespan (gallons or months), and the breadth of contaminants addressed.

2. Certification Coverage (25%)

Certifications from NSF/ANSI and other accredited bodies provide independent verification of manufacturer claims. We score based on the number of relevant certifications held, the standards covered, and whether certifications are current and verifiable in public databases.

3. Cost & Value (20%)

We calculate total cost of ownership, including initial purchase price, replacement filter costs, price per gallon of filtered water, warranty terms, and expected system lifespan. A higher-priced system can still score well here if its long-term value proposition is strong.

4. Installation Complexity (15%)

We evaluate how difficult the system is to install for an average homeowner. Factors include whether professional plumbing is required, tools needed, estimated installation time, and clarity of included instructions.

5. Maintenance Requirements (10%)

This dimension scores the ongoing effort and cost required to keep the system operating effectively. We consider filter replacement frequency, availability and cost of replacement cartridges, system cleaning needs, and indicator systems for filter life.

Scoring Process

Each dimension receives a raw score, which is then multiplied by its weight to produce a weighted score. The five weighted scores are summed to produce a final score out of 100. Products are assigned a rating tier based on their final score:

• 90-100: Excellent - Top-tier performance across all criteria. Strongly recommended.
• 80-89: Very Good - Solid performance with minor limitations. Recommended.
• 70-79: Good - Acceptable performance but notable trade-offs. Worth considering.
• 60-69: Fair - Significant limitations. Only suitable for specific use cases.
• Below 60: Poor - Does not meet our minimum standards. Not recommended.

Update Process

Product reviews are re-evaluated on a 90-day cycle. During each review, we check for:

• Changes in manufacturer specifications
• Newly earned or expired certifications
• Price changes and availability
• User-reported issues or safety concerns
• Product discontinuations or recalls

If a material change is detected, the review is updated immediately rather than waiting for the next cycle.

Independence & Disclosure

Filter Tested maintains complete editorial independence. No manufacturer, distributor, or retailer has input into our ratings, rankings, or written content. We do not accept payment for reviews, placement in recommendations, or favorable coverage. Our business model relies on affiliate commissions, which are disclosed transparently on our Disclosure page. Affiliate relationships never influence our scores.