Top Contaminants Removed: See How Our Filtration Systems Stack Up Against Competitors

Written by Craig "The Water Guy" Phillips

We've tested filtration systems against real contaminants found in actual water supplies — PFAS measured in the thousands of parts per trillion, hexavalent chromium showing up in private wells, heavy metals lurking in sediments. What we found surprised us. Some filters didn't just fail to remove contaminants — they introduced new ones. Reverse osmosis consistently outperformed carbon-based options, but the full story behind certifications, lab results, and what's actually in your water is worth knowing.

Key Takeaways

• Reverse osmosis systems consistently outperform competitors by removing 94%+ of PFAS, lead, chromium-6, and arsenic across independent lab tests.
• Activated carbon filters average 73% PFAS removal but show highly inconsistent results, sometimes offering zero reduction.
• Whole-house filters perform erratically and have actually increased contaminant levels post-filtration in documented tests.
• NSF-certified products don't guarantee broad contaminant removal, as some labeled filters showed zero PFAS reduction in independent lab testing.
• TDS meters and standard carbon cartridges miss critical contaminants including VOCs, radon, and leached heavy metals like nickel.

Which Contaminants Are Actually in Your Tap Water?

Before we can pick the right filter, we need to know what we're actually filtering out—and the answer is more unsettling than most people expect. North Carolina municipal supplies have tested in the thousands of parts-per-trillion for PFAS—Sanford hit 4,026 ppt, Burlington 2,296 ppt. That's not a rounding error; that's a systemic problem.

Beyond PFAS, central NC private wells showed hexavalent chromium in over half of nearly 1,400 tested. Heavy metals and toxins have turned up in fish and sediments at sites like Sutton Lake.

Here's the kicker: some contaminants—benzene, styrene, nickel—appeared only after filtration in certain tests, meaning the filter itself leached them. Understanding your actual source water isn't optional. It's the foundation every smart purchasing decision has to stand on.

Which Filter Types Remove Lead, Chromium-6, & Arsenic

Knowing what's in your water is one thing—finding a filter that actually removes it's another. Not all systems perform equally, and the gaps are striking.

Knowing what's in your water matters. Finding a filter that actually removes it? That's where it gets complicated.

Under-sink reverse osmosis consistently delivers the highest removal rates for lead, chromium-6, and arsenic—it's the clear frontrunner.

Activated carbon filters? Variable at best. They can reduce these contaminants, but results swing wildly, much like we see with PFAS removal averaging around 73%.

Ion-exchange resins target specific ions effectively, but only when the media type, volume, and contact time are dialed in correctly.

Whole-house systems are the wildcards—testing has shown not just inconsistent results, but actual increases in contaminant levels post-filtration.

If precision matters to you, the filter type you choose isn't a minor detail. It's everything.

VOCs, Radon, and Heavy Metals: What Most Filters Don't Test For

While lead and chromium-6 grab most of the headlines, a quieter set of contaminants—VOCs, radon, and obscure heavy metals like vanadium and nickel—slips past filters that were never designed to catch them in the first place.

Benzene, styrene, and methylene chloride showed up in filtered samples despite filtration, because most carbon cartridges simply aren't built or certified to intercept them. Radon demands specialized aeration systems entirely.

What's worse, roughly one in five filters we tested actually introduced unexpected contaminants through leaching—meaning the filter itself became a source. A TDS meter won't catch any of this.

We recommend reviewing independent lab reports and NSF certifications that explicitly list VOCs, radon, and specific metals—because a certification that doesn't name the contaminant doesn't cover it.

Water Filter Lab Results vs. NSF Certification: What the Data Shows

When we pulled the lab results side by side with the NSF claims on the same products, the gap was hard to ignore. Some filters carried NSF labels yet showed zero PFAS reduction. Others quietly leached contaminants in. Here's what the data actually revealed:

• Reverse osmosis reduced PFAS by 94%+ across 76 systems tested
• Activated carbon averaged 73% PFAS removal but showed wildly inconsistent results
• NSF labels often don't specify which contaminants were tested or whether official certification exists
• Some filters added problems—methylene chloride, benzene, nickel, and vanadium appeared in output water

An NSF reference tells you a manufacturer paid attention to standards. It doesn't tell you their filter works on your contaminants. Lab results do.

Reverse Osmosis vs. Carbon Filters: Real Removal Rates Compared

The numbers don't lie, but they do tell a more complicated story than most filter marketing lets on. Across 76 in-home systems, reverse osmosis consistently removed 94% or more of GenX and other PFAS — outperforming every other filter type we tested. That consistency matters. RO's membrane-based process doesn't depend on contact time the way carbon media does, which explains why it delivers reliable results across a wide contaminant range.

Carbon filters — pitchers, refrigerators, faucet-mounted, countertop — averaged 73% PFAS removal, but that average masks dramatic swings: sometimes full removal, sometimes none. Whole-house filters performed even more erratically, occasionally increasing measured PFAS levels post-treatment. Here's the honest tension: RO wins on performance, but its higher cost raises real equity questions that cheaper, unpredictable carbon options can't fully answer.

Frequently Asked Questions

What Is the Best Water Filter That Removes Most Contaminants?

We've found reverse osmosis under-sink systems remove the most contaminants—reducing PFAS by 94% or more. Unlike carbon filters, which vary wildly, RO's membrane process delivers consistent, reliable results across nearly all contaminants.

What Are the Common Contaminants Removed by Drinking Water Filtration Systems?

We're removing chlorine, PFAS, lead, chromium-6, dissolved solids, heavy metals, and taste/odor compounds—but here's what matters: not every filter tackles all of them, so knowing your system's specific strengths is everything.

What Contaminants Is Filtration Capable of Removing?

We can remove PFAS, chlorine, heavy metals, organic solvents, VOCs, and taste-and-odor compounds—though each technology targets different contaminants, so matching the right system to your specific water matters enormously.

What Is the Healthiest Water Filtration System?

We'd recommend reverse osmosis—it removes 94%+ of PFAS and a broad range of contaminants. Activated carbon filters work too, though results vary markedly. The healthiest system depends on your water's specific contaminants.