Pitcher, countertop or under-sink: which water filter do you need?
Start with what's in your water, then match the filter type. Here's how to read the certifications and work out the real cost per gallon.
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Water filters are sold on promises: "removes 99% of contaminants", "lab tested", "pure". The useful questions are narrower. What is actually in your water, which filter is certified to reduce it, and what will it cost to keep running?
Step one: find out what's in your water
If you're on a public water system in the U.S., your utility has to publish an annual water quality report, often called a Consumer Confidence Report (CCR). Search your utility's name plus "water quality report". It lists what was detected and at what levels.
Two things the report can't tell you:
- Lead from your own pipes or fixtures. Lead usually comes from service lines and plumbing inside older homes, not from the treatment plant. Many utilities offer low-cost or free lead testing.
- Private wells. If your water comes from a well, nobody tests it but you. Get a lab test before choosing a filter.
Step two: understand the certifications
The most useful mark on a water filter is a certification to an NSF/ANSI standard, issued by an accredited body such as NSF, WQA, IAPMO or CSA. The standard number tells you what kind of claim it covers:
| Standard | What it covers |
|---|---|
| NSF/ANSI 42 | Aesthetic effects: chlorine taste and odor, particulates |
| NSF/ANSI 53 | Health-related contaminants, such as lead, certain volatile organic chemicals and, for some products, PFOA/PFOS |
| NSF/ANSI 401 | Selected "emerging" compounds, such as some pharmaceutical residues |
| NSF/ANSI 58 | Reverse osmosis systems |
The catch: certification is per contaminant. A filter certified to NSF/ANSI 53 for lead isn't automatically certified for PFAS. Look up the exact model in the certifier's online listing and read the reduction claims line by line.
"Tested to NSF standards" or "meets NSF standards" is not the same as "NSF certified". Only the certifier's own listing confirms it.
Step three: pick the type that fits your kitchen
| Type | Best for | Trade-offs |
|---|---|---|
| Pitcher | Small households, renters, taste and chlorine | Slow to refill, small capacity, frequent filter changes |
| Faucet-mounted | Renters who want filtered water on tap | Doesn't fit every faucet, can slow flow, bulky on the spout |
| Countertop gravity tank | Large batches without plumbing | Takes counter space, filters can be expensive, needs regular cleaning |
| Under-sink (carbon, multi-stage) | Homeowners who want filtered water from a dedicated tap | Needs installation and cabinet space |
| Reverse osmosis (RO) | The widest range of contaminants, including dissolved solids | Sends some water down the drain, removes minerals, needs the most space and maintenance |
A few practical points:
- Pitchers are the easiest start, but check whether the specific pitcher filter carries the certification you need. Many basic pitcher filters cover taste and chlorine only.
- Under-sink systems often use a separate faucet. Check whether your sink has a spare hole or whether you're willing to drill one.
- Reverse osmosis is the heavy option. It's worth it when your report or lab test shows problems a carbon filter isn't certified to handle. It's overkill if all you want is better-tasting city water.
Step four: work out the real cost
The filter price is the smaller part of the cost. Replacement cartridges are where the money goes.
Divide the price of a replacement filter by its rated capacity in gallons to get a cost per gallon, then multiply by how much water your household drinks and cooks with. A cheap pitcher with a short-lived filter can cost more over a year than an under-sink system with long-life cartridges.
Also check:
- Whether replacement filters are easy to buy. Some brands change filter designs; others are widely available.
- Whether there's a change indicator. A timer or flow-based indicator is much easier than remembering a date.
- Rated capacity vs. months. A filter rated for "two months" assumes a certain daily use. Heavy use wears it out sooner.
When a filter isn't the answer
Water softeners and filters solve different problems. Hard water (white scale on kettles and faucets) is calcium and magnesium; a drinking-water filter generally won't stop scale throughout the house. And if a test shows bacteria in well water, you need treatment designed for disinfection, not a carbon filter.
Questions people ask
Do water filter pitchers remove lead?
Some do and some don't. Check the certifier's listing for that exact pitcher filter and look for lead reduction under NSF/ANSI 53.
Do I need reverse osmosis?
Only if your water report or a lab test shows contaminants that a certified carbon filter can't handle, or if you want to reduce total dissolved solids. For chlorine taste and odor, a carbon filter is usually enough.
How often should I change the filter?
Follow the rated capacity or the manufacturer's schedule, whichever comes first. An overdue filter can stop reducing contaminants and may slow your flow to a trickle.