The best way to filter water depends on what you’re trying to remove. Reverse osmosis systems offer the most thorough filtration for home use, capturing everything from lead and nitrates to microplastics and dissolved solids. But a simple activated carbon pitcher filter may be all you need if your main concern is improving taste or removing chlorine. The right choice comes down to your water quality, your budget, and how much maintenance you’re willing to handle.
What’s Actually in Your Water
Before picking a filter, it helps to know what you’re filtering out. Municipal tap water in the U.S. is treated to meet federal safety standards, but that doesn’t mean it’s free of everything you might want to avoid. Common concerns include chlorine and chloramine (added during treatment), lead from aging pipes, nitrates from agricultural runoff, volatile organic compounds, trace pharmaceuticals, pesticides, and increasingly, microplastics and PFAS (sometimes called “forever chemicals”).
Your local water utility publishes an annual Consumer Confidence Report listing what’s in your water and at what levels. If you’re on a private well, you won’t get that report and should have your water tested independently. Knowing your specific contaminants narrows the field fast.
Activated Carbon Filters
Carbon filters are the most common and affordable option. They work by adsorption: contaminants stick to the surface of the carbon as water passes through. You’ll find them in pitcher filters, faucet-mount units, and under-sink systems. They’re effective at removing chlorine, improving taste and odor, and reducing many volatile organic compounds.
Granular activated carbon (GAC) also works well against longer-chain PFAS compounds like PFOA and PFOS. According to the EPA, GAC can be 100 percent effective at removing these chemicals for a period of time, though performance depends on the type of carbon, how fast the water flows through, and how much organic matter is competing for space on the carbon surface. As the carbon becomes saturated, removal rates drop, which is why filter replacement schedules matter so much with these systems.
Where carbon filters fall short is with dissolved minerals, nitrates, and most heavy metals. A basic carbon pitcher won’t do much for lead unless it’s specifically certified for that purpose. If lead is your concern, look for filters tested to NSF/ANSI Standard 53, which covers health-related contaminants including lead, the parasite Cryptosporidium, and chromium. The EPA maintains a consumer tool that lists point-of-use and pitcher filters certified to reduce lead to 5 parts per billion or less.
Reverse Osmosis Systems
Reverse osmosis (RO) is the most comprehensive home filtration method. It forces water through a semipermeable membrane with pores small enough to block particles as tiny as 0.0001 micrometers. That’s small enough to catch microplastics, nanoplastics, dissolved salts, heavy metals, nitrates, and most bacteria.
RO systems are rated by their rejection rate, which is the percentage of a given contaminant the membrane blocks. For nitrates, a typical home RO unit rejects around 85 percent. If your water contains 40 mg/L of nitrate, that brings it down to about 6 mg/L. But if your starting concentration is very high, say 80 mg/L, that same 85 percent rejection still leaves you at 12 mg/L, which is above the federal limit of 10 mg/L. So RO is powerful but not a magic number: your starting water quality still matters.
Most home RO units sit under the kitchen sink and include a small storage tank. They typically pair the membrane with pre-filters (sediment and carbon) to protect the membrane and extend its life. The downside is waste water. RO systems send a portion of water down the drain during filtration, often two to four gallons for every gallon of filtered water produced. They also strip out beneficial minerals like calcium and magnesium, leaving water that tastes flat to some people. Remineralization filters can be added as a final stage to address this.
Removing Microplastics
Microplastics have been found in tap water worldwide, and filtering them out requires knowing how small they are. Standard microfiltration membranes, with pores between 0.1 and 10 micrometers, catch larger microplastic particles along with bacteria and algae. Ultrafiltration uses much smaller pores (0.001 to 0.1 micrometers) and is considerably more effective at capturing smaller fragments.
Nanofiltration, with pores between 0.002 and 0.005 micrometers, removes microplastics and even some nanoplastics. Reverse osmosis goes furthest, filtering anything larger than 0.0001 micrometers. If microplastics are a primary concern, an RO system or a filter specifically rated for sub-micron particles is your best bet. Most standard carbon pitcher filters are not fine enough to reliably catch the smallest microplastic fragments.
Distillation
Distillation works differently from filtration. It boils water into steam and then condenses it back into liquid, leaving behind virtually all dissolved solids, minerals, heavy metals, and most contaminants. It’s extremely effective, but slow and energy-intensive for daily household use.
The trade-off is that distilled water is stripped of calcium, magnesium, and other minerals your body uses. Most people get these minerals primarily through food rather than water, so drinking distilled water won’t cause a deficiency as long as your diet includes enough fruits and vegetables. But the flat taste puts some people off, and countertop distillers produce only a few gallons per day.
Ion Exchange and Water Softeners
Ion exchange systems swap unwanted ions in your water for less problematic ones. Traditional water softeners use this process to replace calcium and magnesium (the minerals that make water “hard” and leave scale on fixtures) with sodium ions. The resin beads inside the unit hold sodium and release it as they grab calcium and magnesium from the water passing through.
Specialized ion exchange resins can also target heavy metals. Chelating resins are designed to form stable bonds with heavy metal ions while letting sodium, calcium, and magnesium pass through, making them useful in situations where specific metal contamination is the problem. These systems are more common in whole-house setups and require periodic resin regeneration or replacement.
How Certification Standards Help
The fastest way to compare filters is by their NSF/ANSI certification. Three standards cover most home concerns:
- NSF/ANSI 42 covers aesthetic improvements: chlorine, taste, odor, and particulate reduction.
- NSF/ANSI 53 covers health-related contaminants with over 50 specific claims, including lead, Cryptosporidium, volatile organic compounds, and chromium.
- NSF/ANSI 401 covers emerging contaminants like prescription drugs, over-the-counter medications, herbicides, and pesticides, with up to 15 specific reduction claims.
A filter certified to Standard 42 alone will improve how your water tastes but won’t protect you from lead or other health hazards. If you’re concerned about specific contaminants, look for Standard 53 or 401 certification and check whether the filter is tested against the particular substance you care about. Certification means an independent lab verified the manufacturer’s claims, not just that the company says it works.
Cost and Maintenance
The purchase price of a filter is only part of the equation. Replacement filters and membranes add up over time, and a filter that isn’t replaced on schedule can actually worsen your water quality as trapped contaminants accumulate.
Pitcher filters are the cheapest to buy, typically under $40 for the pitcher itself, but replacement cartridges run $15 to $40 every two to three months. That puts annual filter costs between $60 and $240. Under-sink systems, including carbon and RO units, cost more upfront but have longer replacement cycles: $30 to $100 every six to twelve months for the filters. Whole-house systems carry the highest maintenance cost at $50 to $200 every six to twelve months, plus occasional professional servicing.
RO membranes typically last two to three years before needing replacement, but the carbon pre-filters and post-filters in the system need swapping more frequently. Ignoring replacement schedules is the single most common reason home filtration systems underperform.
Choosing the Right System
For most households on treated municipal water where the main goal is better-tasting water, a quality carbon filter certified to NSF/ANSI 42 is sufficient and affordable. If your water report shows elevated lead, nitrates, or other specific contaminants, step up to a system certified to NSF/ANSI 53 or consider an under-sink RO unit for the most thorough protection.
If you’re on well water with unknown contaminants, or if PFAS contamination is a concern in your area, reverse osmosis paired with a granular activated carbon pre-filter covers the widest range of threats. For hard water causing scale buildup, a whole-house ion exchange softener handles the mineral issue, though you may still want a point-of-use filter at the kitchen tap for drinking water quality.
No single filter type removes everything. The most effective home setups combine methods: carbon for chlorine and organic chemicals, RO or ultrafiltration for dissolved solids and microplastics, and ion exchange for hardness or targeted metals. Match the system to what’s actually in your water rather than buying the most expensive option and hoping it covers all bases.