At-home kit · $50 · ~15 minutes
Microplastic test kit for filtered water.
Almost no consumer water filter is certified for microplastic removal. Brita, PUR, and ZeroWater are NSF-certified for chlorine, taste, and select heavy metals. Reverse osmosis works by physics. Berkey claims >99.9% but the testing is mostly in-house. The only honest way to know which filter actually catches plastic is to test its output. The microplastic test kit ships with two tests — one for the tap input, one for the filter output.
What each major filter actually does
| Filter | Mechanism | Microplastic claim |
|---|---|---|
| Brita pitcher | Activated carbon + ion exchange | Not NSF-certified for microplastics. May catch some. |
| PUR pitcher/faucet | Activated carbon + chelating agent | Not NSF-certified for microplastics. |
| ZeroWater 5-stage | Ion exchange + carbon | Tighter than Brita but no microplastic certification. |
| Berkey gravity | Ceramic + carbon block | Claims >99.9%; verification is mostly in-house. |
| Reverse osmosis | 0.0001 µm membrane | Physics: pore size is 10,000x smaller than smallest microplastic. |
| Fridge dispenser cartridge | Activated carbon (varies) | Some NSF 401 certified; most are not. |
The before/after test that actually answers the question
Two tests per kit, one of each:
- 1Test 1 — Input. Pour 100 mL of cold tap water from the same faucet that feeds your filter, before filtration. This is your baseline. Without it, the output number is meaningless.
- 2Test 2 — Output. Pour 100 mL of filtered water directly from your filter into the kit's viewing cup. Use the same protocol exactly. Compare to the input filter side-by-side under the blue LED.
- 3Verdict. Output near-blank = filter works for plastic. Output similar to input = filter does not meaningfully remove plastic at your house. Output denser than input = filter is shedding particles (replace it).
Per-filter teardowns
- Does reverse osmosis remove microplastics →
- Does Brita remove microplastics →
- Does PUR remove microplastics →
- Does ZeroWater remove microplastics →
- Does Berkey remove microplastics →
FAQ
Can I test whether my water filter actually removes microplastics?
Yes — and it's the highest-value way to use the kit, because filter manufacturers rarely make microplastic-specific claims. Run one test on your tap water (input) and one on your filter's output. The delta is your filter's real-world microplastic removal. Two tests per kit makes this a single-purchase A/B.
Which filters actually remove microplastics?
Reverse osmosis (~0.0001 µm pore size, ~10,000x smaller than the smallest microplastic) consistently removes near-everything when the system is installed correctly. Granular activated carbon pitchers (Brita, PUR) catch some larger particles but aren't certified for microplastics — a 2022 Pivokonsky study showed they were less effective than tighter membrane filters. Berkey claims >99.9% but third-party verification is thin. The kit lets you verify yours instead of trusting the marketing.
Is fridge water (door dispenser) filtered enough?
Depends on the filter cartridge. Most fridge cartridges are activated carbon, usually NSF 42 certified for chlorine and taste — not microplastics. Some newer ones (the LG LT1000P, certain Samsung models) carry NSF 401 certification which includes some microplastic claims. Either way, the only honest answer is to test the output. Cartridges past their replacement window often shed particles.
Does an old filter add microplastics instead of removing them?
Yes, this happens. Activated carbon beds can release carbon fines once saturated. Plastic-housed filters (most fridge cartridges, pitcher filters) shed micro-fragments from the housing as they age. If you're past your cartridge's stated lifespan, swap it before testing — or test before and after to confirm the new filter is doing more than the old one.
Should I test the input water too?
Always. The single-sample output number is meaningless without a baseline. The pattern is: 100 mL of unfiltered tap (input) → 100 mL of filter output → compare. If both are dense, the filter isn't doing the job. If the input is dense and the output is near-blank, it's working. Two tests per kit is exactly enough for this.
How long after I install a new filter should I test?
Run the manufacturer's break-in flush first (usually 2–3 pitcher pours or 5–10 gallons through an RO system) to clear any production residue. Then test. A brand-new filter not flushed can return a falsely dense filter because of plastic dust from the cartridge housing.