Every year, Columbus Water Works publishes an Annual Water Quality Report — a document that most residents never read. It's dense, technical, and written in regulatory language that makes it easy to skim past the parts that actually matter for your family's health.

We read it so you don't have to.

This guide breaks down exactly what was found in Columbus tap water in 2024, what each contaminant means for your health, and what you can do about it.

Columbus Water Works serves approximately 1.1 million people across Columbus and its surrounding communities — making it one of the largest municipal water systems in Ohio and the entire Midwest. The system draws water primarily from the Hoover, O'Shaughnessy, and Griggs reservoirs, which are fed by the Olentangy and Scioto rivers.

That scale matters. When a contaminant enters the Columbus water supply, it affects over a million people simultaneously. And while Columbus Water Works does a commendable job meeting EPA regulatory standards, "meeting the legal limit" and "safe for everyone" are not the same thing — a distinction we'll return to throughout this article.

Here's what Columbus Water Works detected in the 2024 reporting period, along with the legal limits set by the EPA:

Trihalomethanes (TTHMs) are a class of disinfection byproducts formed when chlorine — used to kill bacteria and viruses in the water supply — reacts with naturally occurring organic matter in the source water. The four main TTHMs are chloroform, bromodichloromethane, dibromochloromethane, and bromoform.

Columbus detected TTHMs at 38 parts per billion (ppb), which is less than half the EPA's maximum contaminant level of 80 ppb. That sounds reassuring — until you look at what the research actually says.

The International Agency for Research on Cancer (IARC) classifies chloroform (the most common TTHM) as a possible human carcinogen. Long-term exposure to TTHMs has been associated in epidemiological studies with increased risk of bladder cancer, colorectal cancer, and adverse reproductive outcomes including low birth weight and miscarriage. The EPA's legal limit was set based on what's technically achievable for water systems — not on what's biologically safe for sensitive populations.

The Environmental Working Group (EWG) sets a health guideline for TTHMs of just 0.15 ppb — more than 250 times stricter than the EPA limit. Columbus's detected level of 38 ppb is roughly 250 times higher than EWG's recommended threshold.

HAA5s are another group of chlorine disinfection byproducts — specifically five haloacetic acids including monochloroacetic acid, dichloroacetic acid, and trichloroacetic acid. Like TTHMs, they form when chlorine interacts with organic matter in the source water.

Columbus detected HAA5s at 22 ppb, well below the EPA's 60 ppb limit. However, dichloroacetic acid — one of the five — is classified as a probable human carcinogen by the EPA itself. Long-term exposure has been linked to liver, kidney, and reproductive effects in animal studies.

EWG's health guideline for HAA5s is 0.1 ppb. Columbus's detected level is 220 times higher.

Nitrate enters the Columbus water supply primarily through agricultural runoff from the Olentangy watershed — fertilizers, animal waste, and septic systems all contribute nitrogen compounds that eventually reach surface water and groundwater.

Columbus detected nitrate at 1.2 parts per million (ppm), which is comfortably below the EPA's 10 ppm limit. However, nitrate is particularly dangerous for infants under 6 months old, in whom it can cause methemoglobinemia — commonly called "blue baby syndrome" — a potentially fatal condition where nitrate interferes with the blood's ability to carry oxygen.

Pregnant women and people with certain enzyme deficiencies are also considered at elevated risk. If you have an infant at home or are pregnant, filtered water for formula preparation and drinking is strongly recommended regardless of whether levels are "below the limit."

Lead is not added to Columbus water — it enters the water after it leaves the treatment plant, by leaching from lead service lines, lead solder in older plumbing, and brass fixtures. Columbus Water Works has been working to replace lead service lines across the city, but thousands of older homes — particularly those built before 1986 — may still have lead plumbing components.

There is no safe level of lead exposure, according to the CDC. Even low-level lead exposure in children causes irreversible neurological damage, reduced IQ, behavioral problems, and developmental delays. In adults, lead exposure is linked to hypertension, kidney damage, and reproductive harm.

If your Columbus home was built before 1986, or if you're unsure about your service line material, testing your tap water for lead is essential. A whole house filter alone won't remove lead — you need a reverse osmosis system or a certified lead-reduction filter at the point of use.

As discussed in our hard water guide, Columbus water is classified as hard to very hard, with hardness levels ranging from 120 mg/L in some city zones to 180 mg/L in suburban areas. Hardness is not a health risk, but it causes significant economic damage — scaling appliances, reducing water heater efficiency by up to 30%, and requiring far more soap and detergent to achieve basic cleaning.

For most Columbus households, hardness is the single most impactful water quality issue in terms of annual cost.

Columbus Water Works maintains a chlorine residual in the distribution system to prevent bacterial regrowth as water travels through miles of pipes to reach your home. This is standard practice for large municipal systems and is required by the EPA.

However, chlorine at the tap — up to 4 ppm in some areas — is a significant source of taste and odor complaints in Columbus. More importantly, that residual chlorine is what reacts with organic matter in your home's plumbing to continue forming TTHMs and HAA5s after the water leaves the treatment plant.

Chlorine also damages hair and skin with regular shower and bath exposure, stripping natural oils and disrupting the skin's microbiome. A whole house carbon filter removes chlorine at the point of entry, protecting every faucet and shower in your home.

This phrase appears throughout water quality reports, and it's designed to be reassuring. It shouldn't be.

EPA legal limits are not health-based thresholds. They are regulatory compromises that balance public health goals against what's technically and economically feasible for water utilities to achieve. The Safe Drinking Water Act explicitly allows the EPA to set limits higher than what would be ideal from a pure health standpoint when achieving lower levels would be too costly.

The Environmental Working Group's Tap Water Database applies health-based guidelines derived from peer-reviewed science — not regulatory feasibility. By EWG standards, Columbus water exceeds health guidelines for TTHMs and HAA5s by factors of 100–250x, even while remaining fully compliant with EPA regulations.

This doesn't mean Columbus tap water is immediately dangerous for healthy adults. It means that long-term, cumulative exposure — drinking the same water every day for decades — carries risks that the legal framework isn't designed to fully address, particularly for vulnerable populations.

PFAS (per- and polyfluoroalkyl substances) — sometimes called "forever chemicals" because they don't break down in the environment or the human body — have been detected in water sources across Ohio, including some wells and surface water near industrial sites in Central Ohio.

Columbus city water has not reported PFAS detections above the EPA's new 4 parts per trillion (ppt) limit as of the 2024 report. However, private well owners in Franklin and Delaware counties near industrial corridors, airports, or military facilities should test specifically for PFAS, as these sources are not covered by municipal water reports.

PFAS exposure has been linked to thyroid disease, immune system disruption, certain cancers, and developmental problems in children. Standard carbon filters do not remove PFAS — you need a reverse osmosis system or a filter specifically certified for PFAS reduction (NSF/ANSI 58 or 53).

While Columbus tap water is technically safe for most healthy adults under current EPA standards, certain groups face elevated risk from the contaminants described above:

• Infants and young children: More vulnerable to lead, nitrate, and disinfection byproducts due to developing nervous systems and higher water intake relative to body weight
• Pregnant women: TTHMs and HAA5s have been associated with adverse birth outcomes; nitrate poses risk to fetal oxygen supply
• Immunocompromised individuals: People undergoing chemotherapy, organ transplant recipients, and those with HIV/AIDS may be more susceptible to microbial risks and chemical sensitivities
• Elderly residents: Cumulative lifetime exposure to carcinogens is a greater concern; kidney function declines with age, reducing the body's ability to process contaminants
• Residents of pre-1986 homes: At elevated risk for lead exposure from aging plumbing

The good news is that every contaminant identified in Columbus water has an effective filtration solution. Here's what works for what:

A whole house activated carbon filter installed at your home's point of entry removes chlorine, chloramines, TTHMs, HAA5s, and volatile organic compounds from every tap in your home. This is the most impactful single upgrade for Columbus city water users, addressing the most widespread contaminants and protecting your appliances from chlorine damage simultaneously.

Explore whole house filter options →

An under-sink reverse osmosis (RO) system at the kitchen tap provides the highest level of contaminant removal for drinking and cooking water. RO membranes remove lead, nitrates, PFAS, arsenic, fluoride, and most dissolved solids. An alkaline RO system adds beneficial minerals back to the water after filtration, improving taste and pH.

For households with infants, pregnant women, or immunocompromised members, an RO system is the most important investment you can make in water safety.

A salt-based water softener addresses Columbus's significant hardness problem, protecting appliances, reducing energy costs, and improving skin and hair health. Best paired with a whole house carbon filter for comprehensive city water treatment.

If you're on a private well in rural Franklin or Delaware County, iron, manganese, and hydrogen sulfide are common additional concerns. A dedicated iron filter using Katalox or Birm media addresses these issues before they reach your home's plumbing.

The only way to know exactly what's in your specific tap water is to test it. Municipal water quality reports reflect averages across the entire distribution system — your water may be better or worse depending on your neighborhood, the age of your pipes, and your proximity to the treatment plant.

Pure Aqua Columbus offers a free in-home water test that measures hardness, iron, pH, chlorine, and other key parameters. You'll get same-day results with a clear explanation of what we found — and honest recommendations for what, if anything, needs to be addressed.

Schedule your free water test →

Read our full Columbus water quality guide →

Columbus tap water meets all EPA regulatory standards and is considered safe for most healthy adults under current federal guidelines. However, it contains detectable levels of disinfection byproducts (TTHMs at 38 ppb, HAA5s at 22 ppb) that exceed the Environmental Working Group's health-based guidelines by significant margins. For infants, pregnant women, immunocompromised individuals, and residents of older homes with potential lead plumbing, additional filtration — particularly a reverse osmosis system — is strongly recommended. "Meets legal standards" and "optimal for health" are not the same thing.

The 2024 Columbus Water Quality Report detected the following key contaminants: TTHMs (trihalomethanes) at 38 ppb, HAA5s (haloacetic acids) at 22 ppb, nitrate at 1.2 ppm, lead in older homes with lead service lines, hardness at 120–180 mg/L, and chlorine residual up to 4 ppm. All detected levels are below EPA legal limits. However, TTHMs and HAA5s exceed the Environmental Working Group's health-based guidelines, and lead has no safe exposure level according to the CDC.

Columbus city water has not reported PFAS detections above the EPA's new 4 parts per trillion limit as of the 2024 Annual Water Quality Report. However, PFAS have been detected in some private wells and groundwater sources near industrial sites in Central Ohio. Private well owners in Franklin and Delaware counties — particularly near airports, military facilities, or industrial corridors — should test specifically for PFAS. If detected, a reverse osmosis system or an NSF/ANSI 58-certified PFAS filter is required for removal, as standard carbon filters are not effective against PFAS.

• Columbus Ohio Water Quality: What's Really in Your Tap Water
• PFAS and Forever Chemicals in Ohio Drinking Water
• Is Columbus Tap Water Ruining Your Hair and Skin? The Chlorine Problem
• Hard Water in Columbus Ohio: Signs, Costs & How to Fix It
• Alkaline Reverse Osmosis Drinking Water Systems
• Whole House Water Filters for Columbus, Ohio
• Water Softeners for Columbus, Ohio
• Water Softeners for Dublin, Ohio
• Water Softeners for Westerville, Ohio
• Water Softeners for Hilliard, Ohio
• Schedule a Free Water Test