How to Filter Microplastics from Tap Water: What Works

Written by: Scott Steveson, Specialist, Wellness Quality Institute

Key Takeaways

• Reverse osmosis, certified solid carbon block filtration, and distillation are the most effective methods for removing microplastics from tap water.

• NSF/ANSI 401 certification is the only reliable way to verify a filter’s microplastic reduction claims; marketing language alone does not confirm performance.

• Boiling water followed by a coffee filter can remove up to 90% of microplastics in hard water but remains a partial solution and does not address nanoplastics.

• Reverse osmosis is the only widely available method that consistently removes both microplastics and nanoplastics, though it requires more upfront investment and uses more water.

• For expert guidance on reducing plastic exposure and achieving plastic-free certification, visit The Wellness Quality Institute.

The Direct Answer: What Works Right Now

The three most effective ways to filter microplastics from tap water are reverse osmosis (membranes with an effective pore size of approximately 0.0001 microns, which is smaller than 0.001 microns), certified solid carbon block filtration (mechanically filters particles down to 0.5 microns, as certified under NSF/ANSI Standards 42 and 53), and distillation. Boiling water traps microplastics most effectively in hard water (≥120 mg/L CaCO3), removing at least 80% of nanoplastics and microplastics, but even soft water (<60 mg/L CaCO3) can remove about 25%. Boiling still leaves many particles behind, so it works only as a partial fix.

Filtration Methods That Actually Remove Microplastics

Reverse Osmosis (RO): The Gold Standard

Reverse osmosis pushes water through a semi-permeable membrane, similar to an extremely fine screen, with pores around 0.0001 microns (0.1 nanometers), not 0.001 microns. That pore size blocks microplastics, nanoplastics, and most other contaminants including heavy metals and PFAS (per- and polyfluoroalkyl substances, a group of long-lasting industrial chemicals).

RO is the most effective method available for both microplastic and nanoplastic removal. Systems can be verified under NSF/ANSI 58 for particle reduction, and some models carry NSF/ANSI 401 certification specifically for microplastic reduction. That certification means an independent third party tested that exact model and confirmed its performance.

The tradeoffs are significant and worth weighing. Older, conventional reverse osmosis systems typically waste roughly 3–4 gallons of water per gallon filtered, while some inefficient units can waste up to 10 gallons per gallon. Installation is flexible, since RO systems can sit under the sink, in a basement or garage, or on the counter as plug-in units. RO also removes beneficial minerals, although some systems remineralize the water. Under-sink reverse osmosis systems typically cost $150–$500 or more, with annual replacement filter costs of about $50–$200 per year, and some sources report higher ranges.

Solid Carbon Block Filtration: The Practical Middle Ground

Water passes through a compressed block of carbon with pore sizes typically ranging from 0.5 to 10 microns (0.5 microns is the finest rating for cyst reduction). The block physically traps particles, and the carbon surface also adsorbs, or chemically attracts and holds, chlorine and other chemicals that affect taste and odor.

This method works well for microplastics down to the filter’s pore size, yet performance varies widely by design. The key distinctions are:

• Choose solid carbon block, not granular activated carbon, which uses loose granules that water can flow around.

• Confirm a pore size of 1 micron or less.

• Check for NSF/ANSI 401 certification for that specific model.

Solid carbon block filters rated at 0.5–1 µm do not remove nanoplastics below approximately 0.5 µm, though they may partially capture larger nanoplastics. Standard pitcher-style filters that use only granular activated carbon (GAC) and ion exchange are generally not effective for microplastic removal, while tighter carbon block filters or pitchers certified under NSF/ANSI 401 can remove microplastics down to about 0.5 microns. Solid carbon block systems for countertop or under-sink use typically cost $50–$300 upfront, with annual replacement cartridge costs of $20–$60.

Ultrafiltration (UF): A Growing Alternative

Ultrafiltration uses hollow fiber membranes, which are thin tubes with microscopic pores, with pore sizes around 0.01–0.1 microns. That range sits between carbon block and reverse osmosis in filtration fineness. Some whole-house UF systems use membranes with pore sizes as fine as 0.015 microns, which block particles, bacteria, and very fine sediment while maintaining good flow rates.

Ultrafiltration (UF) membranes can remove microplastics and some nanoplastics, although effectiveness for nanoplastics depends on membrane pore size and UF does not create an absolute barrier. Fewer certified models exist compared to RO, and nanoplastic removal remains less proven. Typical countertop UF systems cost about $100–$400.

Distillation: High Removal, High Energy Use

Distillation removes microplastics and nanoplastics by boiling water and condensing the steam, leaving plastic particles behind in the boiling chamber because they do not vaporize at 100°C. Effectiveness depends on good system design and proper operation, and some nanoplastics may escape capture or reenter the water through plastic components.

Distillation is very effective but slow and energy-intensive. It strips beneficial minerals and often produces flat-tasting water. Countertop distillers typically cost between $100 and $600, with some budget models under $100 and premium models over $1,000, plus ongoing electricity costs.

The Boiling and Coffee Filter Method: A Helpful Backup

A 2024 study published in ACS ES&T Water found that boiling hard water (containing >120 mg/L calcium carbonate) causes polystyrene, polyethylene, and polypropylene microplastics to become encrusted with limescale (calcium carbonate), removing at least 80% of particles sized 0.1–150 μm, which a simple coffee filter can then trap. The study reported up to 90% removal in very hard water and about 25% removal in soft water.

This method depends on limescale formation, so it only works with hard water. Soft water gains very little benefit from boiling. The process also leaves other contaminants in place, and the coffee filter step remains essential because boiling alone does not remove particles. Treat this as a science-backed trick and a partial measure. Test your water hardness first and rely on certified filtration for your main protection.

Comparison Table: How the Main Methods Stack Up

The table below summarizes pore size, microplastic removal ability, and typical costs so you can quickly compare your options.

Method	Pore Size	Microplastic Removal	Approximate Cost
Reverse Osmosis	~0.0001 microns (0.1 nm)	Yes, microplastics and nanoplastics (look for NSF/ANSI 58 or NSF/ANSI 401)	$150–$500+ system; $50–$200/yr filters
Solid Carbon Block (≤1 micron)	0.5–10 microns	Yes for microplastics if NSF/ANSI 401 certified; not nanoplastics	$50–$300 system; $20–$60/yr filters
Ultrafiltration	0.01–0.1 microns	Yes for microplastics; partial for larger nanoplastics	$100–$400 system
Distillation	N/A (boiling + condensation)	Yes, microplastics and nanoplastics	$100–$600 system + electricity
Boiling + Coffee Filter	~20 microns (coffee filter)	Partial, up to 90% in hard water; ~25% in soft water; not nanoplastics	Minimal

NSF/ANSI 401 Certification: How to Read the Label

NSF/ANSI 401 is a certification standard from NSF International and the American National Standards Institute. In plain language, it means an independent organization tested a specific filter model and confirmed it reduces certain emerging contaminants, such as pharmaceuticals, herbicides, and pesticides, to defined levels. The same process can verify microplastic reduction claims for that model.

Certification always applies to a specific model, not an entire brand. A company may sell one certified filter and several uncertified versions. A label that says “removes microplastics” without NSF/ANSI 401 certification remains a marketing claim without independent proof.

Use this simple process to check whether your filter is certified:

1. Visit the NSF International website and open the water filter certification database.

2. Search by brand name and model number.

3. Look for “microplastic reduction” or “NSF/ANSI 401” in the listing.

Certification gives you the strongest signal of real performance. If a filter lacks it, treat the microplastic claim as unverified.

Explore ways to reduce plastic exposure or pursue plastic-free certification for your products.

Brita and Microplastics: What Their Filters Actually Do

Standard Brita pitchers and faucet filters use activated carbon filtration, which targets chlorine, taste, and odor rather than physically trapping microplastic particles. Brita’s standard pitcher filters (for example, OB03) are not NSF/ANSI 401 certified for microplastic reduction, and Brita does not claim microplastic removal for these products. Brita’s Elite (OB06) and Total360 models do hold NSF/ANSI 401 certifications for microplastics reduction.

If you want a pitcher-style filter that reduces microplastics, choose one with a 0.5-micron filter and NSF/ANSI 401 certification, or consider a countertop ultrafiltration system. Some newer pitcher lines may offer stronger filtration, yet you still need to verify certification before assuming any pitcher removes microplastics.

How to Match a Filter to Your Home and Budget

Your best choice depends on budget, living situation, and how much removal you want.

• Maximum removal with under-sink space: Choose a reverse osmosis system with NSF/ANSI 401 certification. RO is the only common method that reliably removes nanoplastics as well as microplastics.

• Renting or need portability: Consider a countertop ultrafiltration system or a certified solid carbon block filter. Look for NSF/ANSI 401 certification and a pore size of 1 micron or less.

• Very tight budget: Use a certified carbon block pitcher as a starting point and understand its limits. It will not remove nanoplastics, and you must verify certification for that exact model.

• Hard water and want a low-cost supplement: Use the boiling and coffee filter method as an add-on. It can remove up to 90% of microplastics in hard water but still leaves nanoplastics and other contaminants.

Before buying any filter, check three details: third-party certification (NSF/ANSI 401), pore size (1 micron or less for microplastic reduction), and annual replacement filter costs.

Everyday Habits to Cut Microplastic Exposure

Filtration makes the biggest difference, and daily choices also help reduce exposure.

• Skip bottled water. A 2018 study by Mason et al. in Frontiers in Chemistry found microplastics in 93% of bottled water samples, at roughly twice the concentration found in tap water. The most common polymer was polypropylene from bottle caps, which points to the packaging as a major source.

• Use glass or stainless steel containers for drinking water and food storage, especially for hot liquids.

• Avoid heating food in plastic containers. Heat speeds up plastic breakdown and increases particle shedding.

• Reduce plastic in your kitchen. Choose glass storage containers, skip plastic wrap when possible, and favor fresh foods over heavily plastic-packaged options.

The Bottom Line on Microplastic Filtration

Filtering microplastics from tap water is realistic when you choose proven methods and verified products. Reverse osmosis offers the strongest protection and remains the only widely available method that consistently removes nanoplastics. Certified solid carbon block filtration works well for microplastics when you confirm NSF/ANSI 401 certification for the specific model. Distillation is highly effective yet energy-intensive, and the boiling plus coffee filter method only helps with hard water and functions as a backup strategy.

The most reliable step is checking for third-party certification instead of trusting marketing language. If a filter does not carry NSF/ANSI 401 certification for microplastic reduction, treat any claim as unproven.

The Wellness Quality Institute (WQI) supports brands that want to back up their water product claims with solid data through its Plastic-Free Pathway Verification program. Learn about Plastic-Free Pathway Verification and how it supports credible microplastic claims.

Frequently Asked Questions

Will a Brita filter remove microplastics?

Standard Brita pitchers use activated carbon filtration, which improves taste and removes chlorine but does not reliably trap microplastic particles. As noted earlier, Brita’s standard pitcher filters lack NSF/ANSI 401 certification, while its Elite and Total360 models hold that certification. If microplastic removal is your goal, choose a filter with a pore size of 1 micron or less and confirmed NSF/ANSI 401 certification for that specific model.

What is the best water filter for microplastics?

Reverse osmosis ranks among the most effective methods for removing microplastics and nanoplastics, with membranes around 0.0001 microns (0.1 nm) or less than 2 nm, achieving over 99% removal when the membrane and seals remain intact. For a lower-cost approach, a solid carbon block filter with NSF/ANSI 401 certification and a pore size of 1 micron or less will reduce microplastics, though it will not capture nanoplastics. Ultrafiltration systems sit between these options in cost and effectiveness. In every case, verify certification for the exact model, not just the brand.

Does boiling water remove microplastics?

Boiling helps only under specific conditions. As described earlier, a 2024 study showed that boiling hard water causes microplastics to become coated with limescale so a coffee filter can trap them. In soft water, the same process removes only about 25% of particles. Boiling alone, without the coffee filter step, does not remove enough particles. This method also leaves nanoplastics and other contaminants in place, so treat it as a supplement rather than your main strategy.

What is NSF/ANSI 401 certification?

NSF/ANSI 401 is an independent certification standard that confirms a specific water filter model reduces emerging contaminants. These contaminants include pharmaceuticals, herbicides, and pesticides, which the filter must reduce to defined levels. “NSF/ANSI 401 certified” means an independent organization tested that exact model and confirmed its performance claims. Certification is model-specific, so one certified product in a brand’s lineup does not guarantee that other models are certified. Always confirm details in the NSF International database by brand name and model number.

Are there water filters that remove nanoplastics?

Reverse osmosis membranes, with pore sizes below 2 nanometers, can achieve over 99.9% removal of nanoplastics, making RO one of the most effective membrane-based methods, although performance depends on membrane integrity and system design. Ultrafiltration systems with pore sizes of 0.01–0.1 microns can remove larger nanoplastics, but effectiveness depends on particle size relative to the membrane pores, and smaller nanoplastics may pass through. Solid carbon block filters and pitcher-style filters generally do not remove nanoplastics.

Is bottled water safer than tap water for microplastics?

Research points in the opposite direction. A 2018 study found microplastics in 93% of bottled water samples, at roughly twice the concentration found in tap water. The most common polymer was polypropylene from bottle caps, which suggests the packaging itself as a major contamination source. Bottled water does not reliably reduce microplastic exposure, and filtered tap water from a certified system is usually the better choice.

How do I know if my current filter is certified for microplastic removal?

Visit the NSF International website and use the water filter certification database. Search by your filter’s brand name and model number, and look for “microplastic reduction” listed under NSF/ANSI 401. If your filter model does not appear in the database with a microplastic reduction claim, the manufacturer’s marketing language has not been independently verified.

Read Next

• Microplastics in Water: Risks, Filters & Smarter Choices

• Microplastics in Water: What Brands Need to Know

• Microplastics in Drinking Water: Testing Explained

• Microplastics Testing Limits and How to Judge the Evidence

• Microplastics in Drinking Water: What the Science Says