Water Filtration Technologies Compared

Removes: 95-99% of TDS including heavy metals (lead, arsenic, mercury), fluoride, nitrates, sodium, PFAS, bacteria, viruses, and most dissolved solids.

Misses: Some VOCs and dissolved gases can pass through the membrane. Chlorine degrades RO membranes, so a carbon pre-filter is required.

Pros: Most comprehensive single-technology removal. Produces very pure water. Well-documented performance data.

Cons: Wastes 2-4 gallons per gallon produced (improving with newer systems). Removes beneficial minerals. Slow production rate (storage tank needed). Requires periodic membrane and filter replacement.

Cost: $0.02-$0.05 per gallon after $200-$500 system cost. Membrane replacement every 2-3 years (~$50-$80).

Removes: Chlorine and chloramine (taste/odor), many VOCs, some pesticides and herbicides, some PFAS (especially with carbon block). NSF 42 and sometimes NSF 53 certified.

Misses: Does not remove dissolved metals effectively (lead removal only with specialized carbon blocks). Poor fluoride, nitrate, and TDS removal. Limited bacteria/virus removal.

Pros: Inexpensive. No water waste. Simple pitcher, faucet-mount, or under-sink installation. Preserves minerals. Fast flow rate.

Cons: Performance degrades as carbon saturates. Must be replaced on schedule. Inconsistent PFAS removal across brands and types. GAC (granular) is less effective than solid carbon blocks.

Cost: $0.01-$0.03 per gallon. System cost $20 (pitcher) to $150 (under-sink carbon block).

Removes: Chlorine (via redox reaction), heavy metals (lead, mercury, copper) to a degree, and inhibits bacterial growth within the filter media. Uses copper-zinc granules.

Misses: Limited effectiveness against VOCs, PFAS, pesticides, fluoride, and nitrates. Not a standalone solution for comprehensive filtration.

Pros: Long media life. Functions in hot water (unlike carbon). Bacteriostatic -- inhibits bacterial growth in the filter bed.

Cons: Best used as a pre-filter or in combination with carbon. Limited third-party testing data compared to RO and carbon. Performance claims often exceed independent verification.

Cost: $0.01-$0.02 per gallon as part of a multi-stage system.

Removes: Water hardness (calcium, magnesium) via cation exchange. Specialized resins remove specific metals: lead, barium, radium. Deionization resins remove most dissolved ions.

Misses: Standard softening resins do not remove bacteria, viruses, VOCs, or PFAS. Adds sodium to water (in sodium-cycle softeners).

Pros: Highly effective for targeted contaminant removal. Specialized lead-removal resins can reduce lead to below 1 ppb.

Cons: Requires regeneration (salt for softeners, chemical for DI). Resin beds need replacement. Selective -- must match resin to target contaminant.

Cost: $0.02-$0.04 per gallon for whole-house softening. Point-of-use lead-specific cartridges $30-$60, last 6-12 months.

Removes: Bacteria (E. coli, coliform), viruses, and protozoa (Giardia, Cryptosporidium) through DNA disruption. 99.99% inactivation at proper dosage.

Misses: Zero chemical removal. Does not remove heavy metals, VOCs, PFAS, chlorine, fluoride, or any dissolved contaminant. Requires pre-filtration for turbid water (particles shield microbes).

Pros: No chemicals added. No water waste. No taste or odor impact. Low operating cost. Effective against chlorine-resistant organisms like Cryptosporidium.

Cons: Only addresses biological contamination. Requires electricity. Lamp replacement annually (~$50-$100). Water must be pre-filtered to be clear for UV to penetrate effectively.

Cost: $0.01 per gallon. System cost $150-$400. Annual lamp replacement.

Removes: Virtually everything: heavy metals, minerals, bacteria, viruses, PFAS, nitrates, fluoride, salts, and most dissolved solids. Produces water as pure as RO or purer.

Misses: VOCs with boiling points lower than water can carry over with steam. Some systems include a carbon post-filter to catch these.

Pros: Highest purity achievable. No membrane to replace. Simple, proven technology. Works on any water source.

Cons: Very slow (4-6 hours per gallon for countertop units). High energy consumption (~$0.25-$0.35 per gallon in electricity). Produces flat-tasting water. Removes all minerals.

Cost: $0.25-$0.35 per gallon (energy). Countertop units $100-$400. No recurring filter costs beyond occasional cleaning.