Quick Guide to Certified Water Filters for Arsenic

Arsenic is a naturally occurring contaminant that can enter groundwater, and eventually drinking water, through natural geological deposits as well as industrial or agricultural activity. Because arsenic in drinking water is colorless, tasteless, and odorless, it often goes undetected but arsenic exposure is associated with long-term health risks. One of the most reliable ways to reduce arsenic exposure is by using NSF certified filters, which are tested to NSF/ANSI standards to verify contaminant reduction performance.

Before choosing an arsenic water filter, it’s important to test your water to determine whether arsenic is present — and in what form — so that treatment decisions are based on data, not assumption.

Table of Contents:

1. What Are the Relevant Standards for Arsenic?
2. How Do I Know If I Have Arsenic in My Water?
3. Water Filters Certified for Arsenic Reduction
4. Which Arsenic Filter Is Right for Me?
5. The Importance of Testing
6. What’s the Takeaway?

This guide continues our Tips for Taps series on NSF Certified Filters:

Quick Guide to Certified Water Filters for Lead
Quick Guide to Certified Water Filters for PFAS 
Quick Guide to Certified Water Filters for Fluoride 
Quick Guide to Certified Water Filters for VOCs

What Are the Relevant Standards for Arsenic?

Arsenic reduction is typically certified under:

• NSF/ANSI Standard 53: for arsenic (primarily arsenic V)
• NSF/ANSI Standard 58: for reverse osmosis systems capable of reducing arsenic

Remember:

• Certification is contaminant-specific
• Some systems reduce arsenic V (arsenate) but not arsenic III (arsenite)
• Pre-filtration oxidation may be required to effectively treat certain forms of arsenic

The All-in-One Guide to Arsenic in Drinking Water

Arsenic III vs. Arsenic V: Why It Matters

Arsenic in drinking water typically exists in one of two forms:

• Arsenic V (arsenate)
• Arsenic III (arsenite)

Most certified filters — especially those tested under NSF/ANSI Standard 53 — are designed to reduce arsenic V, which is easier to remove. However, arsenic III is more difficult to treat and may not be effectively reduced without additional treatment steps.

In many cases, arsenic III must be oxidized into arsenic V before filtration can work effectively. Some treatment systems include this step, while others do not.

Because of this, knowing not just whether arsenic is present — but also which form it exists in, via an Arsenic Speciation Water Test — can be critical when selecting the right treatment system.

What Are NSF, WQA, and IAPMO?

The NSF (National Sanitation Foundation), WQA (Water Quality Organization) and IAPMO (International Association of Plumbing and Mechanical Officials) are three different organizations that grant certifications to water treatment devices that meet standards for performance and safety.

NSF, WQA, and IAPMO certifications are all of equal stature and any of their badges are intended to offer the consumer greater confidence when selecting a filter. What matters is that the product in question has undergone a thorough evaluation by one of these specific third parties that specialize in testing and certification. 

NSF/ANSI Certifications Explained

Why Certification Matters

Filters certified to NSF/ANSI standards have undergone testing to confirm the filtration device in question can effectively reduce these contaminants to specified levels, in addition to other considerations. Without certification, there’s no guarantee that a filter’s performance matches its marketing claims.

NSF/ANSI standards address the following:

• Material safety
• Structural integrity
• Specific contaminant reduction claims

In addition, certified products may be subject to ongoing monitoring and factory audits as part of the certification process.

How Do I Know If I Have Arsenic in My Water?

Arsenic cannot be detected by taste, smell, or appearance. The only way to know if it is present in your water is through laboratory testing.

Testing is especially important because:

• Arsenic levels can vary widely by location
• Different forms of arsenic require different treatment approaches

Ready to test your tap water for arsenic? Tap Score offers a variety of ways to test: 

Or, opt for a more complete picture of your water quality that includes arsenic, opt for the Advanced City Water Test, or the Advanced Well Water Test:

Testing before treatment ensures you select a treatment system that is appropriate for your water’s unique chemistry.

Water Filters Certified for Arsenic Reduction

This is an incomplete list of products certified for the reduction of arsenic in drinking water. It includes the brand, product name, SKU, and certifying body.

Filter Cartridges Certified for Arsenic Reduction

• 3M Under Sink RO Water Filter Cartridge
  (SKU: 3MROP411) NSF
• CB Tech Countertop Kit
  (SKU: CBTAS) NSF
• Multipure Aquaperform Filter
  (SKU: CB11As) NSF

Reverse Osmosis Systems Certified for Arsenic Reduction

• Aquasana SmartFlow® RO Reverse Osmosis System
  (SKU: AQ-SFRO) WQA
• AquaTru Carafe
  (SKU: AT-100) IAPMO
• Aquion Ultrarefiner Elite Reverse Osmosis System
  (SKU: 51565) NSF
• Brondell H2O+ Capella Reverse Osmosis Undersink System
  (SKU: RC250) WQA
• Everpure Conserv RO-75E High Efficiency RO System
  (SKU: 4CC) NSF
• Hellenbrand Millennium MRO-35
  (SKU: S1448RS) NSF

Which Arsenic Filter Is Right for Me?

Choosing the right water filter is always a balance of:

• Your water’s chemistry
• Your household needs and preferences

Factors to consider when making a decision include:

• Filter’s effectiveness against arsenic (and other contaminants)
• Installation type (under sink, countertop, whole home)
• Maintenance and replacement requirements
• Flow rate and daily usage
• Cost over time

Different systems (e.g., reverse osmosis vs. adsorptive media) operate differently and may be better suited to specific situations.

Important: We strongly recommend testing your water before making any treatment choices. Test strips cannot be trusted to accurately measure arsenic concentration.

Comparing Treatment Options for Arsenic

Different filtration technologies reduce arsenic in different ways:

• Reverse Osmosis (RO)
  Widely used and often certified under NSF/ANSI 58, RO systems can effectively reduce arsenic — particularly arsenic V — and are commonly installed under the sink. They work by forcing water through a membrane with tiny pores that block dissolved contaminants like arsenic while allowing water to pass through.
  
• Adsorptive Media (e.g., activated alumina, iron-based media)
  These point-of-use filters remove arsenic by binding it to a treatment media and are typically certified under NSF/ANSI 53. Performance depends on water chemistry and may vary by system.
  
• Whole House (Point-of-Entry) Systems
  Designed to treat all water entering the home, these systems may use specialized treatment media to bind arsenic, but are less commonly certified for arsenic reduction than point-of-use systems.

The most effective option depends on your water chemistry, including pH, competing ions, and the form of arsenic present.

The Top 4 Home Water Filter Technologies Explained

The Importance of Testing

Even the best filter is only effective if it matches your water’s specific contaminants.

Before investing in treatment, always start with a certified laboratory water test. This will tell you:

• Whether arsenic is present
• The concentration
• The form (where applicable)

This information is critical for selecting an appropriate and effective treatment system.