Start withyour water,then pick the filter.
Buying guides for drinking-water filters, reverse osmosis, whole-house systems, softeners and well treatment. We match each product to the problem in your water and the certification that proves it handles it.
Choose by water problem
Test first, then treat. Each section starts with what is in the water and which system class removes it.
Drinking-water filters
Pitchers, faucet, countertop and under-sink
Reverse osmosis
Tank, tankless and countertop RO
Whole-house & softeners
Point-of-entry filters and softeners
Well water
Iron, sulfur, UV and well testing
Testing & parts
Test kits, TDS meters and cartridges
Installation & maintenance
Housings, fittings, pumps and service tools
Understand your water
Compare tank-style under-sink RO systems by certified reduction claims, usable storage, feed-water conditions, replacement filters and space under the sink.
- 02
Home Water Test Kit vs Certified Laboratory Test
Water testing
- 03
How to Choose a Whole-House Water Filter
Whole-house filters
- 04
Pitcher vs Under-Sink Water Filter: Cost, Capacity and Performance
Pitcher vs under-sink
- 05
Reverse Osmosis vs Carbon Filter: Which Problem Does Each Solve?
RO vs carbon
- 06
Salt-Based Softener vs Salt-Free Water Conditioner
Hard-water treatment
Water Filtration questions, answered
Does a tank-style RO system run out of water?
The storage tank holds a finite supply. Compare its usable capacity and recovery information in the manufacturer's manual with your household's peak use.
Read: How to Choose a Tank-Style Reverse Osmosis System →Can a home water test kit replace a certified lab?
Not for every contaminant. Choose a state-certified laboratory for bacteria, nitrate and metals when a reliable concentration is needed.
Read: Home Water Test Kit vs Certified Laboratory Test →What flow rate do I need for a whole-house filter?
Most homes need 6 to 12 gallons per minute at peak. Count fixtures that run at once and check the filter's rated flow at an acceptable pressure drop.
Read: How to Choose a Whole-House Water Filter →Are pitcher filters as good as under-sink filters?
Some pitchers carry strong NSF/ANSI 53 and 401 certifications. The difference is mostly capacity, convenience and cost per gallon, not quality.
Read: Pitcher vs Under-Sink Water Filter →Does a carbon filter remove fluoride?
Standard activated carbon does not meaningfully reduce fluoride. Reverse osmosis or activated alumina is used for fluoride.
Read: Reverse Osmosis vs Carbon Filter →Does a salt-free conditioner soften water?
No. It may reduce scale formation, but it does not remove hardness minerals by ion exchange.
Read: Salt-Based Softener vs Salt-Free Water Conditioner →Certification-first water advice
A contaminant counts as removed only when an independent certification listing says so for that exact model.
Each guide says who the system suits, who should look elsewhere, and what to check before you buy.
Brands cannot buy a review or a spot on a list. Partner codes save you money; they never decide what we recommend.
Prices are dated, codes are updated across the site at once, and pages are revised when a product, standard or rule changes.
The water filtration and treatment index
- 01Drinking-water filtersPoint-of-use filters for the kitchen: pitchers, faucet mounts, countertop units and under-sink carbon systems.2 pages
- 02Reverse osmosisUnder-sink tank and tankless RO, countertop RO, remineralization stages and membranes.2 pages
- 03Whole-house & softenersSediment, carbon and specialty-media systems at the main line, salt-based softeners and salt-free conditioners.4 pages
- 04Well waterIron and manganese filters, sulfur treatment, UV disinfection and well-specific testing.2 pages
- 05Testing & partsLab test kits, strips, TDS and hardness meters, replacement cartridges and installation parts.2 pages
- 06Installation & maintenanceFilter housings, fittings, valves, drain saddles, booster pumps, UV lamps and service tools.0 pages