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Is Sioux City Water Safe to Drink?
Municipal water system · 2024 data · official source
This is the safety page for Sioux City — how hard the water is (and what that costs) lives on the Sioux City water hardness page · see how Sioux City compares across all of Iowa on the Iowa hardness guide · or browse every Iowa city by safety status on the Iowa water quality page.
Sioux City's water has Perfluorohexane sulfonate (PFHXS) above the EPA legal limit. See the breakdown below and consider a filter rated for that contaminant.
What's in Sioux City's water
Detected contaminants reported for Sioux City Water Supply (EPA system ID IA9778054).
Source: EWG tap water database (Aug 2026).
Perfluorohexane sulfonate (PFHXS) exceeds the EPA legal limit. This is worth investigating — a filter rated for that contaminant may be appropriate.
How to read this table: the legal limit (the EPA's Maximum Contaminant Level (MCL)) is the enforceable safety line — it's what regulators actually require. The EWG guideline column is a much stricter, voluntary health benchmark (often 100–1000× lower than the legal limit). Many contaminants sit below the legal limit but above the EWG line — that's common nationwide and means the water is still legally safe, not that it's dangerous.
| Contaminant | Typical level | EPA legal limit | EWG guideline | Status |
|---|---|---|---|---|
| Bromodichloromethane | 17.3 ppb | unregulated | 0.06 ppb | Above EWG |
| Chloroform | 30.7 ppb | unregulated | 0.4 ppb | Above EWG |
| Dibromoacetic acid | 1.88 ppb | unregulated | 0.03 ppb | Above EWG |
| Dibromochloromethane | 8.88 ppb | unregulated | 0.1 ppb | Above EWG |
| Dichloroacetic acid | 10.1 ppb | unregulated | 0.2 ppb | Above EWG |
| Haloacetic acids (HAA5) | 22 ppb | 60 ppb | 0.1 ppb | Below limit |
| Haloacetic acids (HAA9) | 46.9 ppb | unregulated | 0.06 ppb | Above EWG |
| Nitrate | 0.328 ppm | 10 ppm | 0.14 ppm | Below limit |
| Perfluorohexane sulfonate (PFHXS) | 20.8 ppt | 10 ppt | 0.001 ppt | Above limit |
| Perfluoropentane sulfonic acid (PFPeS) | 6.32 ppt | unregulated | 1 ppt | Above EWG |
| Radium, combined (-226 and -228) | 0.6 pCi/L | 5 pCi/L | 0.05 pCi/L | Below limit |
| Total PFOS and PFOA | 4.37 ppt | unregulated | 0.007 ppt | Above EWG |
| Total trihalomethanes (TTHMs) | 57.6 ppb | 80 ppb | 0.15 ppb | Below limit |
| Trichloroacetic acid | 9.85 ppb | unregulated | 0.1 ppb | Above EWG |
Levels are system-wide utility averages. The legal limit is the EPA's Maximum Contaminant Level (MCL). EWG also flags 16 contaminant(s) as exceeding its own stricter (non-legal) health guideline — shown as an informational note only, not a safety claim.
Not sure what these levels mean for your health? Read our complete contaminants guide — what's detected vs. what matters, and how to read the numbers.
What actually matters in Sioux City's water
Most of the numbers in the table are below the legal limit and aren't worth your worry. Here's the honest read on the ones people actually ask about in Sioux City:
Why the limit exists: The limit protects infants from "blue baby syndrome" (methemoglobinemia). Infants under six months convert nitrate to nitrite and lack the enzyme to reverse it, so their blood can't carry oxygen. Cases occur above 10 mg/L, not at or below.
Who it matters most for: Infants under 6 months (especially formula-fed).
Source: EPA MCL / HC MAC
Why the limit exists: Trihalomethanes are disinfection byproducts. Long-term exposure above the limit is associated with liver, kidney, and central nervous system problems plus an increased risk of cancer (most consistently bladder). The limit is a deliberate trade-off: you can't remove them without abandoning disinfection, which would risk far worse microbial disease.
Source: EPA MCL / HC MAC
Why the limit exists: Haloacetic acids are disinfection byproducts associated with an increased risk of cancer at sustained elevated exposure. Same trade-off as TTHMs — the limit balances cancer risk against the necessity of disinfection.
Source: EPA MCL / HC MAC
Why the limit exists: Trihalomethanes are disinfection byproducts. Long-term exposure above the limit is associated with liver, kidney, and central nervous system problems plus an increased risk of cancer (most consistently bladder). The limit is a deliberate trade-off: you can't remove them without abandoning disinfection, which would risk far worse microbial disease.
Source: EPA MCL / HC MAC
Why the limit exists: Trihalomethanes are disinfection byproducts. Long-term exposure above the limit is associated with liver, kidney, and central nervous system problems plus an increased risk of cancer (most consistently bladder). The limit is a deliberate trade-off: you can't remove them without abandoning disinfection, which would risk far worse microbial disease.
Source: EPA MCL / HC MAC
Why the limit exists: Haloacetic acids are disinfection byproducts associated with an increased risk of cancer at sustained elevated exposure. Same trade-off as TTHMs — the limit balances cancer risk against the necessity of disinfection.
Source: EPA MCL / HC MAC
Why the limit exists: Trihalomethanes are disinfection byproducts. Long-term exposure above the limit is associated with liver, kidney, and central nervous system problems plus an increased risk of cancer (most consistently bladder). The limit is a deliberate trade-off: you can't remove them without abandoning disinfection, which would risk far worse microbial disease.
Source: EPA MCL / HC MAC
Why the limit exists: Haloacetic acids are disinfection byproducts associated with an increased risk of cancer at sustained elevated exposure. Same trade-off as TTHMs — the limit balances cancer risk against the necessity of disinfection.
Source: EPA MCL / HC MAC
Why the limit exists: Haloacetic acids are disinfection byproducts associated with an increased risk of cancer at sustained elevated exposure. Same trade-off as TTHMs — the limit balances cancer risk against the necessity of disinfection.
Source: EPA MCL / HC MAC
Why the limit exists: PFAS are "forever chemicals" — extremely persistent. The limits exist because several PFAS are linked to cardiovascular, immune, liver, and thyroid effects, elevated cholesterol (PFNA), and increased incidence of certain cancers (kidney/testicular for PFOA, liver for PFOS). Note: the EPA has proposed revising parts of the individual PFAS MCLs; the underlying health-science rationale is unchanged regardless of the current legal number.
Who it matters most for: Pregnant women, infants, and children (developmental and immune effects).
Source: EPA MCL (2024)
Why the limit exists: PFAS are "forever chemicals" — extremely persistent. The limits exist because several PFAS are linked to cardiovascular, immune, liver, and thyroid effects, elevated cholesterol (PFNA), and increased incidence of certain cancers (kidney/testicular for PFOA, liver for PFOS). Note: the EPA has proposed revising parts of the individual PFAS MCLs; the underlying health-science rationale is unchanged regardless of the current legal number.
Who it matters most for: Pregnant women, infants, and children (developmental and immune effects).
Source: EPA MCL (2024)
Why the limit exists: Radium is radioactive; long-term exposure is associated with an increased risk of bone cancer.
Source: EPA MCL
Why the limit exists: PFAS are "forever chemicals" — extremely persistent. The limits exist because several PFAS are linked to cardiovascular, immune, liver, and thyroid effects, elevated cholesterol (PFNA), and increased incidence of certain cancers (kidney/testicular for PFOA, liver for PFOS). Note: the EPA has proposed revising parts of the individual PFAS MCLs; the underlying health-science rationale is unchanged regardless of the current legal number.
Who it matters most for: Pregnant women, infants, and children (developmental and immune effects).
Source: EPA MCL (2024)
Why the limit exists: Haloacetic acids are disinfection byproducts associated with an increased risk of cancer at sustained elevated exposure. Same trade-off as TTHMs — the limit balances cancer risk against the necessity of disinfection.
Source: EPA MCL / HC MAC
Where Sioux City's water comes from — and how it's treated
Source details are in the official annual water quality report linked on this page.
Like every U.S. municipal supply, Sioux City's water is disinfected and monitored against EPA National Primary Drinking Water Regulations, published annually in the Consumer Confidence Report (CCR). If you want to read the raw report for yourself, our how to read your water quality report guide walks you through it line by line.
Water quality vs. water hardness — don't confuse the two
"Water quality" (is it safe to drink) and "water hardness" (how much scale it leaves) are entirely different things — and confusing them leads to bad purchases. Sioux City's water is very hard (26.3 GPG), which has no bearing on its safety — hardness is a cosmetic and appliance concern, not a health one. For what that hardness costs you in scale, appliance wear, and water-heater efficiency, see the Sioux City water hardness page.
If contaminants concern you — add a drinking-water filter
Should you filter Sioux City's water?
The softener handles hardness; a drinking-water filter removes Nitrate and removes Pfas — if Sioux City's reported levels concern you. EPA: Nitrate (above 10 mg/L as nitrogen) can cause "blue baby syndrome" (methemoglobinemia) in infants and is associated with certain cancers at sustained exposure. EPA: PFAS ("forever chemicals") are linked to certain cancers, immune and thyroid effects, developmental issues, and elevated cholesterol. EPA MCL: 4 ppt for PFOA/PFOS. For a full breakdown of what each filter type removes, see best whole-house water filters.
We may earn a commission when you buy through links on our site. This doesn't affect our recommendations. Full disclosure.
When to call a professional
Sioux City's water has Perfluorohexane sulfonate (PFHXS) above the legal limit, so this is the one case where having a professional look at your tap — not just the city-wide average — is genuinely worth it. A licensed water-treatment specialist can test your home's water specifically, confirm whether your plumbing is contributing anything extra, and recommend a correctly-rated filter (for PFAS, a point-of-use reverse-osmosis or granular-activated-carbon system, for example).
Certified, independent results come from a state/province-licensed lab, not a company with a sales incentive — ask for a lab that reports to the EPA or your state.
Frequently asked questions
Is Sioux City tap water safe to drink?
Sioux City water has contaminant(s) above the legal limit. Review the breakdown below before drinking unfiltered.
Who tests Sioux City's water, and how often?
The utility is required by the EPA to test and publish an annual Consumer Confidence Report (CCR), linked on this page.
Where does Sioux City drinking water come from?
See the official annual water quality report linked on this page.
Should I filter Sioux City's tap water?
Yes — a filter rated for the specific contaminant(s) above the limit is worth considering. See the full breakdown for which one matters.
Is Sioux City water hard?
Sioux City water is very hard at 26.3 GPG (450 ppm). Hardness is separate from safety — it affects scale and appliances, not health. See the Sioux City water hardness page for the full picture.
Sources & method
All contaminant levels are drawn from official, published data — EWG tap water database (Aug 2026) (source). We cite the legal limit for each contaminant so you never see a bare scare number.
- · Sioux City — water-quality report we reviewed
- · USGS — Water Hardness
- · EPA — Drinking Water Regulations
- · CDC — Drinking Water
- · EWG — Tap Water Database
- · Our complete contaminants guide (what's detected vs. what matters, how limits are set)
- · How to read your water quality report — line by line
Compare Sioux City to Other Iowa Cities
How Sioux City's water quality stacks up against nearby cities — same Iowa data, same legal limits.
Other Cities With Exceedances
Cities where a contaminant also runs above the legal limit — see how they compare to Sioux City.
Explore More
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💧 Water treatment pros: this page is yours to share
This page helps customers understand what's in their water and whether they need a filter — so they can weigh whether service is worth it. We recommend sharing this page along with our complete contaminants guide in your next quote or follow-up to fully explain the value of your services.