At-home kit · $50 · ~15 minutes
Microplastic test kit for tap water.
The Orb Media survey found microplastics in 94% of US tap samples. Your utility doesn't test for them, so nobody knows the count from your faucet. The microplastic test kit is the at-home version of the same Nile Red protocol the survey used — two tests per box, results you can count with your own eyes in about 15 minutes.
A real tap-water filter from the at-home kit. Each pink dot is a plastic particle stained with Nile Red.
Why test tap water for microplastics at all
Three independent sources put plastic in your tap. Source water (rivers, reservoirs, groundwater) carries atmospheric and runoff-borne microplastics that conventional coagulation and flocculation reduces but does not eliminate. The treatment plant itself uses plastic gaskets, polymer membranes, and polypropylene piping. And the last mile — your home's service line and indoor plumbing — adds particles every year it's in use, especially when the line is PEX, CPVC, or polypropylene.
A 2019 review in Water Research concluded the contribution from plastic distribution piping can equal or exceed the contribution from raw source water in homes with extensive plastic plumbing. If your house was repiped in the last 20 years, the dominant source is almost certainly your own pipes — not the utility.
Your utility doesn't measure any of this. As of 2026 no US water system is required to test for microplastics, the annual Consumer Confidence Report doesn't include them, and California's 2022 monitoring policy (the only one in the country) doesn't surface the data to customers.
How the kit tests tap water
Same four-step protocol as every sample type. The only thing specific to tap water is the collection — pour 100 mL of cold tap into the kit's graduated viewing cup, ideally the first pour after the line has been sitting overnight.
- 1Collect 100 mL of cold tap water. First-pour-of-the-morning gives the highest particle count — that water has been sitting in your home's pipes overnight.
- 2Add the hydrogen peroxide vial. Swirl. Wait 30 minutes. Breaks down organic matter so it doesn't clog the filter or fool the dye.
- 3Add the Nile Red vial. Swirl. Wait 30 minutes. Dye binds to plastic polymers and ignores minerals, salts, dissolved solids.
- 4Push the entire sample through the membrane filter, fast. Plastic particles are trapped on the disc face.
- 5Clip the orange filter to your phone. Shine the blue LED. Photograph. Plastic glows pink. Upload to get a validated particle count.
The four tap-water tests worth running
Cold morning tap. The baseline. Overnight stagnation pulls the most particles off the pipe walls.
Cold flushed tap. Run the cold tap for 2 minutes, then sample. Compare to the morning sample — the difference is plumbing-shed particulate.
Hot tap. Heat accelerates polymer release from any plastic in the path (PEX, dip tubes, water-heater liners). Usually the highest count.
Filter output. Whatever filter you trust — Brita, RO, fridge dispenser — pour its output into the cup. Compare to your cold tap. That delta is the only honest answer to does my filter actually remove microplastics.
FAQ
Can a microplastic test kit detect particles in tap water?
Yes. The kit traps particles down to 1 micron on a 25mm membrane filter and stains them with Nile Red, which fluoresces pink under 450nm blue light. The 2017 Orb Media tap-water survey used the same Nile Red methodology and found microplastic particles in 94% of US tap samples. The at-home version of that protocol catches the same particles on a kitchen counter.
Which tap should I test — cold morning, hot, filtered, or kitchen?
Cold tap, first thing in the morning, from the kitchen. That sample has been sitting in your home's pipes overnight and picked up whatever they shed — it's the highest-particle sample you can take. Run the second test on hot tap or on your filter output to compare.
How many milliliters of tap water does one test need?
100 mL — about 3.5 ounces. The kit includes a graduated viewing cup so you don't need a separate measuring tool. Two tests per kit, so you can run a cold/hot pair or a tap/filter pair from a single box.
Does the kit work on well water?
Yes, the chemistry is the same. Well water on average has fewer source-borne particles than surface-fed municipal water, but home plumbing (PEX, PVC, plastic-lined pressure tanks) still adds particles. Test it the same way: cold tap, first pour of the morning.
What count is 'normal' for tap water?
Published tap-water counts range from low single digits to a few hundred particles per liter, depending on which size class the study counts. Our internal blank (distilled, lab-clean) returns fewer than 5 particles on the filter. Anything materially above that is real microplastic load — the interesting question becomes which sample in your house has the most.
Is testing tap water for microplastics legally meaningful?
Not yet. The EPA added microplastics to Contaminant Candidate List 6 in April 2026, but there is no enforceable Maximum Contaminant Level, no required utility reporting, and no legal definition of 'too much.' The kit gives you a count for your own decision-making — not a regulatory measurement.