Filtered water is tap water that has passed through a treatment barrier: carbon that adsorbs chemicals and tastes, membranes that reject dissolved solids, screens that catch particles, or some stack of the three. The term covers everything from a fridge pitcher to a whole-house system, which is why it means so little on a label and so much once you know which barrier produced it.
The barriers that do the filtering
Three mechanisms cover nearly all home filtration. Mechanical screens and sediment cartridges physically strain out particles: sand, rust, cloudiness. Activated carbon adsorbs chlorine, many taste-and-odor compounds and a range of organic chemicals onto its enormous internal surface. Membranes, with reverse osmosis at the fine end, reject dissolved solids that pass untouched through both of the others: salts, nitrates, arsenic, lead in its dissolved form. Every product sold as a water filter is some packaging of these mechanisms, and its honest capability is set by which ones it contains.
Filtered versus bottled versus boiled
Bottled water is a subscription to someone else's filtration plus trucking, at a running cost per gallon that home filtration undercuts quickly for a household drinking it daily. Boiling kills microorganisms and does nothing else: minerals, metals and chemicals stay right where they were, slightly concentrated if anything. Home filtration is the only one of the three that removes what your specific supply contains, on your counter or your main line, at marginal cost after the hardware. The sensible comparison is not filtered versus pure; it is filtered versus what your tap delivers unfiltered, which is knowable.
Know what needs filtering before choosing how
The right filtration method depends entirely on what is in the water. Every community water system publishes an annual Consumer Confidence Report, and the EPA maintains a finder for locating yours, so a city household can read its actual supply before buying anything; well owners test independently. Chlorine taste points to carbon, particles to sediment screens, dissolved-solids concerns to reverse osmosis at the drinking tap. And filtered water is not only for drinking: shower water carries the same chlorine to skin and hair, which our best filtered shower head for hard water guide addresses for bathing specifically.
Questions people ask about filtered water
Is filtered water better than bottled water?
For a household drinking it daily, filtration matched to your supply costs far less per gallon and removes what your water actually contains, without the plastic and trucking.
Does boiling water do the same job as filtering?
No. Boiling kills microorganisms but removes no chemicals, metals or minerals; if anything it concentrates them slightly. Filtration and boiling solve different problems.
Is all filtered water the same?
Not remotely. A pitcher's light carbon pass and a reverse osmosis membrane produce very different water. What was removed depends entirely on the barrier used.
How do I know what my water needs filtered out?
Read your utility's annual Consumer Confidence Report, which the EPA maintains a finder for, or test the water directly if you are on a private well.