How whole-house carbon, under-sink reverse osmosis, and under-sink carbon filters compare against common regulated contaminants.
Data current as of July 2026
🔍Straight from EPA
🧪Real Lab Results
📅Updated Quarterly
🏠Local Expertise
There are three common categories of home water filtration, and they're not interchangeable — each is meaningfully better at some contaminants than others. This is general guidance on system types, not a specific product recommendation.
Whole-House Carbon
Installed at the main water line, treats all water entering the home. Effective against disinfection byproducts and VOCs; only partial protection against metals, PFAS, and inorganics.
Under-Sink Reverse Osmosis
Installed at a single tap, typically the kitchen sink. The most broadly effective single technology against metals and PFAS, in addition to disinfection byproducts and VOCs — but only treats water from that one tap.
Under-Sink Carbon
Similar coverage to whole-house carbon, but only at a single tap rather than the whole home.
What carbon filters are effective against
Activated carbon (whole-house or under-sink) is rated "Yes" for two full categories of regulated contaminants — meaning it's generally effective against every substance in these groups, not just the handful shown in the baseline table below:
Disinfection Byproducts
Total Trihalomethanes (TTHM), Haloacetic Acids (HAA5), Chloroform, Bromoform, Bromodichloromethane, Dibromochloromethane, and related byproducts formed when chlorine reacts with organic matter.
VOCs (Volatile Organic Compounds)
Benzene, Toluene, Xylene, Vinyl Chloride, Trichloroethylene (TCE), Tetrachloroethylene (PCE), Carbon Tetrachloride, 1,2-Dichloroethane, Chlorobenzene, MTBE, and the broader family of industrial solvents and fuel-related compounds EPA regulates under this category.
Chlorine Taste & Odor
Free and total chlorine — the most common reason people install any home filter at all, regardless of what else is on file for their area.
Carbon is only partially effective against metals (lead, arsenic, chromium-6, copper, uranium), PFAS, and inorganics (nitrate) — reverse osmosis is the more broadly effective single technology for those. See the category breakdowns on any water quality report for what specifically applies to a given area.
Baseline comparison
The table below is the same comparison shown on every water quality report on this site, for the same 15 commonly-regulated substances used as a baseline.
Contaminant
Whole-House Carbon
Under-Sink RO
Under-Sink Carbon
Total Trihalomethanes (TTHM)
Yes
Yes
Yes
Haloacetic Acids (HAA5)
Yes
Yes
Yes
Chloroform
Yes
Yes
Yes
Chlorine / Taste
Yes
Yes
Yes
Sediment / Turbidity
Yes
Yes
Yes
Trichloroethylene
Yes
Yes
Yes
Tetrachloroethylene
Yes
Yes
Yes
cis-1,2-Dichloroethylene
Yes
Yes
Yes
1,1-Dichloroethylene
Yes
Yes
Yes
Bromoform
Yes
Yes
Yes
Bromodichloromethane
Yes
Yes
Yes
Dibromochloromethane
Yes
Yes
Yes
1,1,2-Trichloroethane
Yes
Yes
Yes
Vinyl Chloride
Yes
Yes
Yes
Carbon Tetrachloride
Yes
Yes
Yes
Benzene
Yes
Yes
Yes
Toluene
Yes
Yes
Yes
Xylene
Yes
Yes
Yes
Lead
Partial
Yes
Partial
Arsenic
Partial
Yes
Partial
Chromium-6 (Hexavalent)
Partial
Yes
Partial
Copper
Partial
Yes
Partial
Combined Uranium
Partial
Yes
Partial
PFOA
Partial
Yes*
Partial
PFOS
Partial
Yes*
Partial
Nitrate
Partial
Yes
Partial
Combined Radium
Partial
Yes
Partial
Coliform Bacteria (indicator)
No
Yes
No
What "Yes*" means for PFAS
Not every reverse osmosis system is certified for PFAS specifically — look for NSF/ANSI 53 or 58 certification for the exact compound you're concerned about (e.g. PFOA or PFOS) rather than assuming any RO system covers it.
Live in this area? Simple Water Heater & Filtration can size a filtration system to whatever's actually on file for your utility.