How to Choose a Water Filter

The right water filter turns cloudy, chlorine-tinged tap water into something you actually want to drink — but the wrong one leaves you swapping cartridges you don’t need while the real problem flows right past. Before you buy anything, you have to know what’s in your water and where you want to treat it.

Start with a water test, not a filter

Every good filtration decision begins the same way: find out what’s actually in your water. If you’re on a municipal supply, your utility publishes an annual Consumer Confidence Report that lists what they detect. If you’re on a private well, no one is testing it for you — that’s on you, and you should test at least once a year for bacteria, nitrates, and hardness.

A simple home test strip or a mail-in lab kit tells you the three things that drive the whole decision: what contaminants you have, how hard your water is, and whether taste or health is your real concern. Chlorine taste is a nuisance; lead and PFAS are a health issue; scale that eats your water heater and faucets is a maintenance issue. Each points to a different filter.

Tip: Hardness (dissolved calcium and magnesium) isn’t a “filter” problem — it’s a softening problem. If your test shows hard water, you likely want a water softener in addition to, not instead of, a filter.

The main filter types, and what each one fixes

Filters aren’t ranked good-to-bad — they’re specialists. The trick is matching the technology to the contaminant it’s certified to reduce. Look for the NSF/ANSI certification number on the box: Standard 42 covers taste and odor (chlorine), Standard 53 covers health contaminants (lead, cysts, some PFAS), and Standard 58 covers reverse osmosis.

Carbon is the workhorse for taste and smell — brands like Brita and PUR dominate the pitcher aisle, while Culligan and Aquasana build the bigger under-sink and whole-house rigs. Reverse osmosis is the heavy hitter: it pushes water through a membrane fine enough to strip out dissolved solids that carbon can’t touch, which is why it’s the go-to for lead, PFAS, and well-water nitrates. The tradeoff is that RO is slower, wastes some water, and strips beneficial minerals (many systems add a remineralization stage back in).

Point-of-use vs. whole-house: where to treat

This is the decision that trips people up. Point-of-use (POU) means you treat water at a single tap — usually the kitchen sink, where you drink and cook. Point-of-entry (POE), or whole-house, means you treat everything as it enters the home, so every shower, tap, and appliance gets filtered water.

Whole-house makes sense when the problem is universal: heavy chlorine you can smell in the shower, sediment clogging aerators throughout the house, or rust staining fixtures. It’s overkill — and expensive — if you only care about drinking water. For most homes, a good under-sink or RO system on the kitchen line covers the health and taste needs for a fraction of the cost. You’ll want basic plumbing tools and possibly new supply lines for a clean under-sink install.

• Only drinking water tastes/smells off? Point-of-use pitcher or under-sink.
• Health contaminant confirmed by a test? Under-sink RO at the kitchen.
• Sediment or chlorine at every tap? Whole-house at the main line.
• Well water with grit? Sediment pre-filter first, then your main filter.

Don’t forget the running cost: cartridges

The sticker price is only half the story. Every filter has a replacement cartridge on a schedule, and a cheap system with expensive, short-lived cartridges can cost more over three years than a pricier system with long-life filters. Check the rated capacity (in gallons) and the manufacturer’s replacement interval before you commit.

A pitcher filter might last 40 gallons (about two months for a family); an under-sink carbon block often runs 6–12 months; RO membranes can last 2–3 years with pre-filters changed on schedule. Set a phone reminder — a neglected filter doesn’t just stop working, it can grow bacteria and dump trapped contaminants back into your glass.

Pick by your situation

Frequently asked questions

Clean water is one of the few home upgrades you notice every single day. Test first, match the filter to the real problem, and factor in the cartridge cost before you buy — then get the right gear and a second opinion from your local independent hardware store. Not sure which system fits your water? Ask us here.