Your tap water may contain dozens of contaminants — some naturally occurring, some from industrial activity, and some added intentionally during treatment. Most are present at levels far below health thresholds, but some can accumulate over time or pose risks to vulnerable populations. Here is a practical guide to the most common water contaminants, where they come from, and which treatment technologies actually remove them.
Chlorine and Chloramines
Source: Added deliberately by municipal water treatment plants to disinfect water and maintain protection throughout the distribution system.
Health concern: Low at typical levels, but affects taste and smell. Chlorine can dry out skin and hair. Disinfection byproducts (trihalomethanes, haloacetic acids) formed when chlorine reacts with organic matter are of greater health concern with long-term exposure.
How to remove: Activated carbon filtration removes free chlorine effectively. Chloramines require catalytic carbon (standard carbon is much less effective against chloramines — check your water report to see which your utility uses).
Lead
Source: Lead pipes, lead solder in joints, and brass fixtures — particularly in homes built before 1986. Lead does not come from the treatment plant; it leaches into water from household plumbing.
Health concern: Serious. There is no safe level of lead exposure. Children and pregnant women face the greatest risk, including developmental delays and neurological damage.
How to remove: NSF/ANSI Standard 53 certified filters, reverse osmosis systems. Standard Brita-style pitcher filters do not reliably remove lead — verify NSF 53 certification specifically for lead reduction.
Nitrates
Source: Agricultural fertilizer runoff, septic system leakage, and natural soil deposits. Most common in rural areas and private wells near farmland.
Health concern: High nitrate levels are dangerous for infants under 6 months, causing methemoglobinemia (blue baby syndrome) — a potentially fatal condition. Also a concern during pregnancy.
How to remove: Reverse osmosis (removes 85-95%), ion exchange systems specifically designed for nitrate removal. Standard carbon filters do not remove nitrates.
Arsenic
Source: Natural geological deposits (common in western US states), industrial discharge, and agricultural pesticides. More prevalent in well water than city water.
Health concern: Long-term exposure linked to cancer, cardiovascular disease, and diabetes. The EPA maximum contaminant level is 10 ppb, but health concerns exist at lower levels with prolonged exposure.
How to remove: Reverse osmosis removes 95-99%. Specialized arsenic-specific filter media (activated alumina, iron-based media) are also effective. Standard carbon filters do not remove arsenic.
Fluoride
Source: Added intentionally by many municipal water systems at 0.7 mg/L to support dental health. Also occurs naturally in some groundwater sources.
Health concern: At recommended levels, fluoride is considered safe and beneficial for dental health by the CDC and WHO. Excessive levels (above 4 mg/L) can cause dental and skeletal fluorosis.
How to remove: Reverse osmosis removes 85-92%. Bone char carbon and activated alumina filters also reduce fluoride. Standard activated carbon filters do not remove fluoride.
PFAS (Per- and Polyfluoroalkyl Substances)
Source: Industrial manufacturing, firefighting foam, non-stick cookware production, and stain-resistant coatings. Extremely persistent in the environment — nicknamed “forever chemicals.”
Health concern: Linked to cancer, thyroid disease, immune system disruption, and developmental issues. The EPA set a maximum contaminant level of 4 parts per trillion for PFOA and PFOS in 2024 — the strictest drinking water standard ever set.
How to remove: Reverse osmosis, high-quality activated carbon filters certified to NSF/ANSI P473 for PFAS reduction. Not all carbon filters remove PFAS — certification matters.
Iron
Source: Natural geological deposits in groundwater, or corroding iron pipes. Most common in well water. Appears as orange or brown staining.
Health concern: Not a health risk at typical levels but causes significant practical problems: stained fixtures and laundry, metallic taste, and damage to water softener resin.
How to remove: Sediment filters for ferric (particulate) iron. Air injection or oxidizing filters for dissolved ferrous iron. Water softeners with fine mesh resin handle iron below 5-8 ppm. Dedicated iron filters for higher concentrations.
Hardness (Calcium and Magnesium)
Source: Natural dissolution of limestone, chalk, and dolomite rock formations as water moves through the ground.
Health concern: None — hard water minerals are safe to drink and may contribute modestly to daily mineral intake.
How to remove: Salt-based ion exchange water softeners physically remove hardness minerals. Salt-free conditioners reduce scale without removing minerals. Reverse osmosis removes minerals but is impractical as a whole-house solution.
Bacteria and Pathogens
Source: Well water contamination from septic systems, surface runoff, or wildlife. City water very rarely contains bacteria if properly treated, but boil water advisories after pipe breaks or flooding can occur.
Health concern: E. coli and coliform bacteria indicate fecal contamination and can cause serious illness. Cryptosporidium and Giardia cause gastrointestinal disease and are resistant to chlorine.
How to remove: UV purification systems kill bacteria and viruses without chemicals and without affecting taste or chemistry. Reverse osmosis membranes remove bacteria and protozoa. Standard carbon filters do not kill or remove bacteria reliably.
Quick Reference: Filter Type vs Contaminant
- Activated carbon: Chlorine, chloramines (catalytic), VOCs, taste, odor
- Reverse osmosis: Lead, nitrates, arsenic, fluoride, PFAS, bacteria, dissolved solids
- UV purifier: Bacteria, viruses, protozoa
- Water softener: Hardness (calcium, magnesium)
- Iron filter: Iron, manganese, hydrogen sulfide
- Sediment filter: Sand, silt, rust, particles
Bottom Line
No single filter removes every contaminant. The right solution depends on what is actually in your water. Test first, identify your specific contaminants, and then select filters certified for those specific substances. Do not rely on marketing claims — NSF certification is the only reliable confirmation that a filter does what it says.
Disclaimer: This guide is for informational purposes. Have your water tested by a certified laboratory to identify specific contaminants before purchasing treatment equipment.