Contaminant encyclopedia

Know the water before you treat the water

Each guide answers three questions plainly: where does it come from, how do you actually test for it, and which certified filter types remove it. No invented lab results here — every claim is linked and dated.

Specs sourced from manufacturer listings · Certified vs claims labeled · WaterVetted does not run lab tests

Browse by topic

Health-effect contaminants (lead, PFAS, arsenic) sit alongside taste-and-odor topics (chlorine, hard water). Start with the one that matches your water report or concern.

PFAS

The "forever chemicals" most public systems were not designed to remove.

Lead

No safe level — but certified filters can remove it.

Chlorine & Chloramine

Safe for public health, annoying in your glass.

Arsenic

Mostly a well-water contaminant — and a serious one.

Nitrate

A farm-country concern, especially for infants.

Microplastics

Found everywhere — but not every filter catches the smallest pieces.

Fluoride

Dental additive that many households still want reduced for taste or preference.

Chloramine

Longer-lasting disinfectant used by many U.S. utilities instead of free chlorine.

VOCs

Volatile organic compounds from industrial solvents and some plastics.

Pesticides

Agricultural runoff residues that show up more often on private wells.

Herbicides

Weed-control chemicals that can migrate into shallow aquifers.

Chromium-6

Hexavalent chromium linked to industrial sites and some aquifers.

Mercury

Heavy metal sometimes present from industrial legacy or dental amalgam contexts.

Cadmium

Toxic metal that can leach from old pipes and industrial soils.

Copper

Corrosion byproduct that stains fixtures and affects taste.

Iron

Common well-water nuisance that stains sinks and tastes metallic.

Manganese

Often pairs with iron in wells; black staining and off flavors.

Hardness (Ca/Mg)

Not a health MCL issue — scale that shortens appliance and RO life.

Sediment & turbidity

Sand, silt and rust particles that clog cartridges and appliances.

Bacteria (coliform)

Private-well risk; filtration is not a substitute for disinfection when positive.

Cysts (Giardia / Crypto)

Protozoan parasites; look for cyst-rated filters or RO.

Asbestos fibers

Legacy cement pipe issue in a minority of older distribution systems.

Radium

Naturally occurring radionuclide in some groundwater regions.

Uranium

Geogenic contaminant in certain Western and Midwestern aquifers.

MTBE

Gasoline additive legacy that still appears in some groundwater plumes.

Pharmaceuticals

Trace medicines; certified reduction claims are still uncommon — check listings carefully.

Trihalomethanes (THMs)

Disinfection byproducts formed when chlorine reacts with organic matter.

Haloacetic acids (HAAs)

Another class of disinfection byproducts tracked in CCRs.

Perchlorate

Rocket-fuel and fertilizer related oxyanion found in some Western waters.

Selenium

Naturally occurring element; excess is a regional groundwater issue.

Barium

Geogenic metal regulated under the Safe Drinking Water Act.

Aluminum

Coagulant residual that can affect clarity and taste in treated water.

Zinc

Metallic taste from plumbing or treatment residuals.

Hydrogen sulfide

Rotten-egg odor common in some wells — often treated before drinking filters.

Total dissolved solids

Broad mineral load; TDS meters help spot filter exhaustion on ion-exchange pitchers.

Microcystin (algae toxins)

Cyanotoxin risk after summer blooms in surface-water systems.

Bromate

Ozonation byproduct monitored by some utilities.

NDMA

Trace disinfection byproduct of emerging concern in some systems.

1,4-Dioxane

Industrial solvent stabilizer; hard for carbon alone — RO is often discussed.

PCBs

Legacy industrial pollutants; rare in finished tap water but still searched.

How to use these pages

Test before you treat when you can. Then match a certified filter type to the contaminant — not a marketing percentage. For lead, insist on NSF/ANSI 53 (or 58 for RO) that names lead for the exact model. See methodology and how to verify NSF listings.