Tap Water vs Filtered Water: What a Filter Changes, and What It Can't

Tap Water vs Filtered Water: The Short Answer

Filtered water is tap water that's been through one more treatment step, the one at your faucet. Whether that step makes your water better comes down to two things: what's actually in the water reaching your glass, and whether your filter is built and rated to remove it.

A filter that isn't matched to a real problem mostly changes the taste. A filter that is matched can cut exposure your utility can't control, like lead picked up from the plumbing inside your own house. That's more useful than "filtered is always better." Below we'll walk through what your utility already does, what a home filter changes, what you give up when you filter, and the few things no filter can fix.

What Your Utility Already Does to Tap Water

If you're on city water, your tap water has already been treated and tested before it reaches you. Most utilities disinfect with chlorine, and there's a practical reason for that beyond killing germs at the plant. According to the EPA's consumer guide to home water filtration, chlorine keeps disinfecting the water as it travels through the pipes to your home.

Your utility also publishes an annual water quality report, often called a Consumer Confidence Report. It lists the contaminants the system detected and how those levels compare with federal standards. It's free, and it's the best first look you'll get at your water.

Where the report stops

The report describes the water your utility delivers. It can't describe the last stretch of pipe between the street and your kitchen, and that's where lead usually comes from. The EPA says lead service lines are typically the most significant source of lead in water, that lead pipes are more likely in homes built before 1986, and that in homes without lead lines the most common problem is brass or chrome-plated brass faucets and lead solder. EPA and the CDC agree there's no known safe level of lead in a child's blood.

Standards also move. EPA set enforceable limits of 4.0 parts per trillion for two PFAS, PFOA and PFOS, and gave utilities until 2029 to fix exceedances. It has since proposed letting systems request two more years, to 2031, and proposed rescinding the limits it set for several other PFAS, according to the EPA's PFAS rule page. Meanwhile, the U.S. Geological Survey estimated, from samples taken between 2016 and 2021, that at least 45% of the nation's tap water could contain one or more PFAS. If that's your main worry, our guide to PFAS in tap water goes deeper.

Tap Water vs Filtered Water, Side by Side

"Filtered" isn't one thing. A pitcher, an under-sink carbon unit and a reverse osmosis system change your water in different ways, so read the right-hand column with your filter type in mind.

Two of those rows catch people off guard, so they're worth a closer look.

The chlorine tradeoff

Taking chlorine out is exactly why filtered water tastes better. University of Nebraska-Lincoln Extension notes that activated carbon can remove both chlorine and chloramines, the disinfectants utilities use. Once they're gone, the filter itself is the thing to watch. The same guide says carbon filters left idle for days, or loaded with organic matter, make an excellent environment for bacterial growth, and that running water through the filter for 30 seconds after it has sat for several hours can limit the bacteria on it. For healthy people, it adds, the harmless bacteria found on most carbon filters pose little risk.

That isn't a reason to skip filtering. It's a reason to keep pitchers, reservoirs and dispensers clean, and to treat the cartridge schedule as part of the deal rather than a suggestion.

The upkeep tradeoff

According to EPA's home filtration guide, activated carbon filters are designed to treat a certain amount of water, and after that they become clogged and ineffective. A cartridge that's months past due isn't giving you filtered water in any meaningful sense. Before you buy, check the replacement schedule and what the cartridges cost, because that's the real price of filtered water over the years you'll own the system. If you're weighing reverse osmosis, add one more line to that math: it uses more water than it delivers, so compare systems on how much goes down the drain.

What a Filter Can't Do

A good filter solves specific problems. It isn't a general safety upgrade, and a few limits are worth knowing before you rely on one.

It isn't a stand-in for boiling in an emergency

If there's a flood, a boil water notice or any reason to suspect germs in your supply, follow your utility's instructions first. EPA's home filtration guide advises boiling water for one minute to kill microbes, or three minutes at altitudes above one mile, then keeping it in a clean, covered container. EPA describes pitcher filters as effective at improving taste, with many also reducing lead and other contaminants. Disinfecting unsafe water is a different job.

It only removes what it's rated for

Two filters can look almost identical and do very different work. EPA points buyers toward units certified by an organization accredited by the American National Standards Institute, because certification to an ANSI/NSF standard requires verification of the unit's contaminant reduction claims. Look for the specific contaminant you care about in the product's certification or performance data, not a vague "removes impurities" line on the box.

It can't tell you what's in your water

A filter changes water. It doesn't measure it. Your annual report or a lab test tells you which problem you're solving, and that decides which filter makes sense. Private well owners don't get an annual report at all, and EPA recommends testing a household well every year for nitrates and coliform bacteria. Our comparison of well water vs city water covers that difference in more detail.

How to Decide Between Tap and Filtered Water

Work through these steps in order and stop once you have your answer.

1. Read your water quality report.

   Search for your utility's Consumer Confidence Report and look for anything detected close to its limit. If you're on a private well, go straight to testing.

2. Think about your plumbing.

   A home built before 1986, a known lead service line or old brass fixtures raises the lead question, and your utility's report can't answer it. In the meantime, EPA's lead guidance is to flush your pipes before drinking by running the tap, taking a shower, doing laundry or running a load of dishes, to use only cold water for drinking, cooking and baby formula, and to ask your utility how long to flush where you live.

3. Test if you're still unsure.

   A lab test turns a guess into real numbers for your own tap. Browse water test kits if you want results before you choose anything.

4. Match the filter to the problem.

   For chlorine taste or smell, a carbon filter such as a countertop filter or an under-sink filter is usually enough. For lead or PFAS, choose a system whose performance data lists that contaminant; many households pick an under-sink reverse osmosis system for drinking water. For chlorine at every tap, showers included, look at a whole house filter.

5. Budget for cartridges.

   Pick a system whose replacement schedule you'll actually keep. The best filter on paper is the one that doesn't sit months past due.

If none of those steps turns up a problem and you like how your water tastes, plain tap water is a perfectly reasonable choice. Our checklist on whether you need a water filter covers the signs that point the other way, and if you're comparing a filter with buying water by the case, see bottled water vs filtered water.

Frequently Asked Questions

Is filtered water healthier than tap water?

It can be, when the filter removes something that's really in your water, like lead from older plumbing. If your water is already clean, the main difference you'll notice is taste. What matters is the match between the filter and the water, not the word "filtered" on its own.

Does filtering remove the minerals in tap water?

It depends on the filter. Carbon doesn't remove calcium and magnesium, the minerals that make water hard, according to University of Nebraska-Lincoln Extension. Reverse osmosis does reduce them: the university's reverse osmosis guide lists both among the contaminants household units remove. For more on that difference, see filtered water vs purified water.