What's in Columbia, MD tap water?
Columbia is Howard County's largest community, and most Columbia homes get their water from the county's public system, Howard County D.P.W. Distribution. This report uses that system's data; see the full Howard County water report for the wider county.
Columbia sits about 26 miles from our Arlington base and is served primarily by Howard County D.P.W. Distribution, which provides water to roughly 286,000 people. It draws from the Potomac River watershed. Most of the DC metro area drinks treated Potomac River water. Because that surface water is heavily disinfected to stay safe across a long distribution system, the contaminants that most often exceed EWG's stricter health guidelines here are chlorination byproducts, alongside unregulated contaminants like PFAS and hexavalent chromium.
Find a local installerHoward County D.P.W. Distribution water quality report, explained
What testing of Howard County D.P.W. Distribution water shows for Columbia, compared with EWG's health guidelines. Being above a guideline is not a legal violation.
Primary water system (EPA)
Howard County D.P.W. Distribution
Serves about 286,000 people
Contaminants EWG most often flags above its health guidelines for the Potomac River watershed:
Larger areas have more than one water system. Enter your exact zip code below for your utility's own EPA record and EWG report.
Measured by the EPA · Columbia, MD
Columbia, MD tap water is fully legal.
It is also 15× the health standard for lead.
Howard County D.P.W. Distribution runs Columbia's water, drawing from surface water and supplying about 286,158 people through 79,084 service connections. A system that size runs a long distribution network, and water spends days in it between the plant and the tap.
Surface water needs heavy disinfection, and chlorine reacting with organic matter in the river is what creates trihalomethanes and haloacetic acids. Those are the contaminants that most often sit above health guidelines here, and they form in the pipes after treatment rather than at the plant.
Every federal limit that applies here is met. Those limits weigh what removal costs. EWG says its health standards are “based only on protecting health and does not consider technical feasibility or the cost of water treatment”. Here is how far apart the two are.
Harm to the brain and nervous system · EPA limit 10 ppb (action level, lowered from 15 ppb, in force November 2027)
Harm to fetal growth and child development · no federal limit exists
Harm to fetal growth and child development · no federal limit exists
The EPA's latest round found 2 PFAS compounds in this supply. Lead sampling put the ninetieth percentile at 3 ppb — meaning nine in ten homes tested below that, and one in ten above it.
Howard County D.P.W. Distribution, on the EPA's record
- Source
- surface water
- Connections served
- 79,084
- People served
- 286,158
- Violations on file
- 3, none health-based
Levels: EPA Fifth Unregulated Contaminant Monitoring Rule (UCMR5, 2023–2025) for PFAS, and the Lead and Copper Rule 90th-percentile result for lead and copper — the highest reported for Howard County D.P.W. Distribution. Health standards: EWG's published drinking water standards, updated February 2025. Levels vary by sampling point and date, and being above a health standard is not a legal violation.
3 contaminants above EWG's health guidelines
Everything EWG found above its guideline in Columbia's water, from testing in 2015-2024. A level can be under the legal limit and still be listed here: EWG's guidelines are set to protect health, not to be easy to meet.
| Contaminant | In this water | EWG guideline | Times over |
|---|---|---|---|
| Haloacetic acids (HAA9) | 38.3 ppb | 0.06 ppb | 638× |
| Total trihalomethanes (TTHMs) | 47.0 ppb | 0.15 ppb | 313× |
| Haloacetic acids (HAA5) | 27.6 ppb | 0.1 ppb | 276× |
Source: EWG Tap Water Database, Howard County D.P.W. Distribution (MD0130002).
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Your tap water is legal. Here’s what’s still in it.
Common in U.S. tap water
Columbia water quality FAQ
Is Columbia, MD tap water safe to drink?
Public water in Columbia meets federal EPA legal limits. But "legal" is not the same as "clean": across the Potomac River watershed, independent testing routinely finds contaminants like total trihalomethanes (TTHMs) and haloacetic acids (HAA5) above EWG's stricter health guidelines. Enter your zip code above to see your exact utility's record.
What contaminants are common in Columbia water?
For the Potomac River watershed, the contaminants that most often exceed health guidelines are total trihalomethanes (TTHMs), haloacetic acids (HAA5), hexavalent chromium (chromium-6), PFAS (forever chemicals) and lead (from older service lines). Your specific levels depend on your utility, which you can look up by zip code above.
Does Sanavia install reverse osmosis systems in Columbia?
Yes. Columbia is roughly 26 miles from our Arlington base and inside our service area. A Sanavia Hydra reverse osmosis system installs under your sink and reduces every contaminant class above, and we'll mail you a free water test kit.
Where does Columbia tap water come from?
Columbia's primary public water system is Howard County D.P.W. Distribution, which serves roughly 286,000 people. It sits in the Potomac River watershed, so its water shares that region's contaminant profile. Larger areas may have more than one utility, so enter your exact zip code above for your own system's EPA record.
Is well water in Columbia tested for these contaminants?
No. Private wells are not covered by municipal testing, so the responsibility falls on the homeowner. If your Columbia home is on a well, nitrate and naturally occurring contaminants are worth testing for specifically, and a reverse osmosis system reduces them at the tap. We'll mail you a free water test kit either way.
Contaminants common in the Potomac River watershed
Each of these is a plain-English guide to a contaminant class common in Columbia and the surrounding Potomac River watershed — what it is, the health context, and what actually removes it.
Reverse osmosis in Columbia, MD
Howard County D.P.W. Distribution treats this water to the federal standard, yet the contaminants listed above still exceed EWG’s stricter health guidelines — Total trihalomethanes (TTHMs), Haloacetic acids (HAA5), Hexavalent chromium (chromium-6) and 2 more. Most of them either pass straight through treatment or form after the plant, in the pipes between it and the tap, which is why the fix has to be at the tap as well.
Lead is the one nothing upstream can fix. It does not arrive from the treatment plant; it comes off the service line and the household plumbing in between, which is why two houses on the same street test differently. A reverse osmosis membrane sits at the end of that run, after every pipe the water has already passed through.
Fit it yourself
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$1,250 installed in Columbia.
Detailed city water reports
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