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Water Filtration Guides

Water Filtration: Cleaner Water at Every Tap

Pitchers, under-sink filters, reverse osmosis and whole-house systems, explained in plain English so you can match the right filter to what is actually in your water.

Start here Compare filters Filter or softener?Certifications FAQ

Filling a reusable water bottle at a kitchen sink

Start here

Essential Water Filtration Guides

The best place to begin if you are choosing your first water filter.

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Types of Water Filters

Pitcher, faucet, under-sink, RO, whole-house and UV, compared side by side.

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What Is Reverse Osmosis?

How RO works, what it removes, how much water it wastes and what it costs.

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Reverse Osmosis Tank Guide

Tank sizes, the right air pressure and how to fix weak flow.

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Remove Iron From Well Water

Types of iron, testing and the best filters.

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Remove Fluoride From Water

Which methods work, which do not, and costs.

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Water Hardness by State

See how hard the water is where you live, with city data.

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Water Softener vs Conditioner

Salt-based or salt-free? Which one fixes your hard water.

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Whole House Water Filter Guide

Sizing, filter types and installation for point-of-entry systems.

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How to Remove PFAS From Tap Water

Which filters work, and which certifications to trust.

Side by side

Which Water Filter Do You Need?

Start with the problem, then pick the filter that solves it.

Your problem	Best filter type	Where it works
Chlorine taste or smell	Carbon (pitcher, faucet, under-sink)	One tap
Lead	Filter certified to NSF/ANSI 53, or RO	One tap
PFAS, nitrate, arsenic, fluoride	Reverse osmosis	One tap
Sediment, chlorine in showers	Whole-house filter	Every tap
Bacteria in well water	UV purifier	Every tap
Scale, spots, dry skin	Water softener (not a filter)	Every tap

Not sure what is in your water? Read your utility’s water quality report or test at home.

Common confusion

Water Filter or Water Softener?

They solve different problems, and many homes need both.

Water filter

Removes contaminants

Carbon, RO and other filters remove chlorine, lead, chemicals and particles. Most do not remove hardness minerals.

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Water softener

Removes hardness

Softeners swap calcium and magnesium for sodium or potassium to stop scale in pipes, heaters and fixtures.

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Trust the label

Certifications to Look For

A filter is only as good as its tested claims. Look for certification from NSF, WQA, IAPMO, CSA Group or UL.

NSF/ANSI 42 · 53 · 58 · 40142: taste, odor and chlorine. 53: health contaminants like lead and PFOA/PFOS. 58: reverse osmosis. 401: emerging contaminants.

Learn more in our guide to types of water filters.

Diagram of how a reverse osmosis system works

Questions

Water Filtration FAQ

Do I need a water filter if I have city water?

City water is treated to meet EPA standards, so a filter is often about taste rather than safety. Some homes still choose one for lead from old pipes, PFAS or chlorine taste. Check your annual water quality report first.

What is the most effective home water filter?

For drinking water, reverse osmosis removes the widest range of contaminants, including lead, nitrate, fluoride and PFAS. For whole-home problems, a whole-house filter matched to your water is best.

Do water filters remove hardness?

Most do not. Carbon filters leave calcium and magnesium in the water. Reverse osmosis removes hardness at one tap, and a water softener treats the whole home.

How often should I replace my filter?

Follow the manufacturer’s schedule. An old filter can stop working or even release what it trapped. Pitcher filters often last about two months, and under-sink cartridges about six to twelve months.