Guides

Water Filter Guides

How to choose, use, and look after a water filter, and which filters suit each need.

Best filters for your needs

Best Reverse Osmosis System for Well WaterSix RO systems with the certified arsenic, nitrate, radium and fluoride claims that matter on a well, plus the testing and pretreatment to do first.

Best Reverse Osmosis System With RemineralizationFour RO systems whose makers list a mineral stage, ranked by our score, with what each is certified to remove and what the mineral stage does.

Best Tankless Reverse Osmosis SystemOnly one reverse osmosis system we score is tankless by its maker's own description, the Waterdrop G3P800, certified by IAPMO R&T for lead, fluoride and PFOA/PFOS.

Best Water Filter for ApartmentsSix filters you can set up without tools or your landlord's permission, all certified for lead, from countertop reverse osmosis to a pitcher.

Best Water Filter for FluorideSeven filters certified to reduce fluoride, from countertop and under-sink reverse osmosis to the one certified pitcher.

Best Water Filter for Hard WaterReverse osmosis reduces hardness at one tap, an ion-exchange softener removes it from the whole house, and a salt-free conditioner only aims to reduce scale.

Best Water Filter for LeadEight filters certified to reduce lead, from a cheap pitcher to reverse osmosis, with the certifier named for each.

Best Water Filter for MicroplasticsSix filters certified to reduce microplastics, from a pitcher to countertop reverse osmosis, and the claims to check before you buy.

Best Water Filter for NitratesThe filters certified to reduce nitrate, what the EPA limit means for infants and well owners, and why boiling makes nitrate worse.

Best Water Filters for Baby FormulaTap, filtered, or bottled: what the CDC and EPA say, and the certified filters for lead, nitrate, and fluoride.

Best Well Water Filtration SystemTest first, then match each problem to the right certified equipment: UV for bacteria, iron filters, softeners, and RO for arsenic, nitrate, and PFAS.

How-to guides

Berkey LawsuitWhy the EPA ordered Black Berkey sales stopped, where the Texas and Puerto Rico cases stand, what Berkey sells now, and what its certification covers.

Boil Water AdvisoryWhy most home filters don't protect you during a boil water advisory, how long to boil, what to do with ice, formula, and dishes, and what to do after.

Brita Filter MoldHow to tell mold from carbon specks and pink Serratia, how to clean a Brita pitcher the way Brita recommends, and how to keep it from coming back.

Does Reverse Osmosis Remove Fluoride? Up to 96%Yes, and certified systems prove it. How much fluoride RO removes, how the certification test works, which systems are certified for it, and what else removes fluoride.

Does Reverse Osmosis Remove PFAS? Over 90%Reverse osmosis removes most PFAS, including the short-chain kinds carbon misses. Here's how much it removes, which systems are certified, and what certification doesn't yet prove.

EPA PFAS RuleThe EPA plans to keep its 4 ppt limits for PFOA and PFOS and drop four other PFAS limits, but as of 13 October 2026 nothing is final and a court ruling is pending.

How Often to Change Water FilterReplacement schedules for pitcher, faucet, fridge, under-sink, RO, whole-house, and UV filters, from the makers' own ratings, plus the signs a filter is spent.

How to Choose a Water FilterA six-step process: test your water, list what to reduce, match the technology, pick a format, check the certification, and compare running costs.

How to Remineralize WaterHow to add minerals back to RO or distilled water with a cartridge, drops, or salt, how much each adds, and what the WHO and BfR say about health.

How to Remove Hard Water StainsHow to dissolve hard water stains on glass, toilets, faucets, and tile, which cleaners to keep off stone, why never to mix with bleach, and prevention.

How to Remove Manganese From WaterWhich treatment removes manganese at which level, from softeners and greensand to oxidation and RO, plus the health limits and what to test first.

Is Reverse Osmosis Water Good for You? Pros and ConsReverse osmosis water is safe to drink and removes contaminants most filters miss. Here's what you lose with the minerals, what the evidence says, and who should add them back.

NSF CertificationWhat NSF certification means, what each NSF/ANSI standard covers, how other certifiers compare, and how to check a listing for the exact model.

Reverse Osmosis vs Carbon FilterReverse osmosis adds certified fluoride, nitrate and arsenic reduction, while a carbon filter keeps minerals, wastes no water and costs less per gallon.

Reverse Osmosis vs Distilled Water: Which Is Better?Distilled water has the fewest minerals, but reverse osmosis makes far more water for less money. Here's what each removes, what each costs, and which to use for drinking and appliances.

Substitute for Distilled WaterWhat to use instead of distilled water for neti pots, CPAPs, humidifiers, irons, batteries, and formula, and how distilled differs from purified water.

What Does Brita Filter Out? Claims by FilterWhat each Brita filter is certified to reduce, from the Elite to the standard, faucet, and Hub filters, and what no Brita filter removes.

What Is Reverse Osmosis? How It Works, ExplainedHow reverse osmosis works, stage by stage: what it removes and misses, how much water it wastes, minerals, and the types of home systems.

Whole House vs Point of Use Water FilterWhat a point of use filter and a whole-house system each do, which contaminants need which, how certification differs, and when to use both.

Why Does My Water Smell Like Rotten Eggs? FixesWhat causes the rotten egg smell, how to tell whether it's the water heater or the well, whether it's safe, and which treatment fits which level.

Why Is My Water Yellow or Brown? Causes and FixesWhat turns tap water yellow or brown on city water and wells, how to tell iron from tannins, whether it's safe, and which fix matches the cause.