# EPA drinking water standards table: every MCL, MCLG, action level and secondary standard a home water test reports against

> Every EPA MCL in one table: arsenic 0.010 mg/L, nitrate 10, lead action level 0.015 (0.010 from Nov 2027), PFOA and PFOS 4.0 ppt, secondary standards.

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| Source | https://ownerspec.com/water/guides/epa-drinking-water-limits-table/ |
| Publisher | OwnerSpec (https://ownerspec.com/) |
| Published | 2026-09-14 |
| Updated | 2026-09-14 |
| Facts verified | 2026-09-14 |

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## Short answer

EPA's National Primary Drinking Water Regulations (NPDWR) set an enforceable Maximum Contaminant Level (MCL) for 16 inorganic chemicals and 4 radionuclide categories, and the tables below list every one in mg/L. The figures a home test panel is measured against most often: arsenic 0.010 mg/L, nitrate 10 mg/L as nitrogen, fluoride 4.0 mg/L, a copper action level of 1.3 mg/L and a lead action level of 0.015 mg/L, which EPA's NPDWR page says drops to 0.010 mg/L on the Lead and Copper Rule Improvements compliance date of November 1, 2027. EPA's 2024 PFAS rule adds an MCL of 4.0 parts per trillion each for PFOA and PFOS, with compliance due April 2029; EPA has proposed moving that date to April 2031 and rescinding the limits on four other PFAS, and neither proposal showed as final on EPA's pages on September 14, 2026. The 15 secondary standards, such as iron 0.3 mg/L and TDS 500 mg/L, are non-mandatory taste and staining guides, not legal limits.

## Fact sheet

- **Answer:** EPA's National Primary Drinking Water Regulations set enforceable MCLs for 16 inorganic chemicals and 4 radionuclide categories, including arsenic 0.010 mg/L, nitrate 10 mg/L and fluoride 4.0 mg/L. The 2024 PFAS rule sets 4.0 ppt each for PFOA and PFOS, and the lead action level is 0.015 mg/L now and 0.010 mg/L from November 1, 2027. Secondary standards such as iron 0.3 mg/L are non-mandatory.
- **Basis:** EPA National Primary Drinking Water Regulations (MCLs, MCLGs and treatment-technique action levels), the 2024 PFAS NPDWR, and EPA's National Secondary Drinking Water Standards.
- **Assumptions:** Figures are the federal limits for public water systems; a state may set a stricter limit and a private well is not covered by any of them; PFOA and PFOS compliance extension and the rescission of four other PFAS limits were both still proposed rules on EPA's pages, last updated July 23, 2026, when this page was written; Lead and copper are treatment-technique rules with a 90th-percentile action level, not an MCL measured at every tap
- **Method:** Every figure copied from the four EPA pages listed under Sources on 2026-09-14, converted to mg/L where EPA prints µg/L or ppt; nothing was tested and no figure comes from a filter maker.
- **Primary source:** [EPA, National Primary Drinking Water Regulations](https://www.epa.gov/ground-water-and-drinking-water/national-primary-drinking-water-regulations) (government or regulatory source)
- **Facts verified:** 2026-09-14
- **Last updated:** 2026-09-14
- **Canonical URL (cite this):** https://ownerspec.com/water/guides/epa-drinking-water-limits-table/

If your lab report already prints an "EPA limit" column beside every result, you can leave now: these are the same numbers, and the only thing this page adds is which of them are enforceable and which are not.

## Which limits are enforceable and which are not?

A Maximum Contaminant Level (MCL) is the highest concentration EPA allows in water delivered by a public water system, and it is enforceable. A Maximum Contaminant Level Goal (MCLG) is the level EPA sets as the health-based target, and it is not enforceable, which is why an MCLG can be zero while the MCL is not.

A Treatment Technique (TT) replaces an MCL where sampling every tap is impractical; lead and copper use one, with an action level triggered at the 90th percentile of sampled taps. A secondary standard is one of the 15 non-mandatory levels on EPA's National Secondary Drinking Water Standards page, set for taste, color and odor.

Every EPA limit applies to public water systems. A private well is outside all of them; the [well water test panel guide](/water/guides/well-water-test-panel/) covers which results to order.

## What are the EPA MCLs for inorganic chemicals?

All values are copied from EPA's National Primary Drinking Water Regulations page and shown in mg/L, the same as parts per million (ppm).

| Contaminant | MCLG (mg/L) | MCL (mg/L) | OwnerSpec guide |
|---|---|---|---|
| Antimony | 0.006 | 0.006 | none |
| Arsenic | 0 | 0.010 | [arsenic in well water](/water/guides/arsenic-in-well-water/) |
| Asbestos | 7 million fibers/L (over 10 µm) | 7 million fibers/L | none |
| Barium | 2 | 2 | none |
| Beryllium | 0.004 | 0.004 | none |
| Cadmium | 0.005 | 0.005 | none |
| Chromium (total) | 0.1 | 0.1 | none |
| Copper | 1.3 | TT; action level 1.3 | [blue-green stains and low pH](/water/guides/blue-green-stains-low-ph-well-water/) |
| Cyanide (free) | 0.2 | 0.2 | none |
| Fluoride | 4.0 | 4.0 | [fluoride in tap water](/water/guides/fluoride-in-tap-water-remove/) |
| Lead | zero | TT; action level 0.015 (0.010 from November 1, 2027) | [lead in tap water](/water/guides/lead-in-tap-water-service-line/) |
| Mercury (inorganic) | 0.002 | 0.002 | none |
| Nitrate (as N) | 10 | 10 | [nitrate in well water](/water/guides/nitrate-in-well-water/) |
| Nitrite (as N) | 1 | 1 | none |
| Selenium | 0.05 | 0.05 | none |
| Thallium | 0.0005 | 0.002 | none |

Nitrate and nitrite are stated as nitrogen. A lab reporting "nitrate as NO3" uses a different scale, so read the unit line before comparing against 10 mg/L; the [nitrate guide](/water/guides/nitrate-in-well-water/) shows the conversion.

## What are the EPA limits for radionuclides?

EPA's NPDWR page prints these in the units a lab uses; the table keeps them and adds mg/L where one exists.

| Contaminant | MCLG | MCL (EPA unit) | MCL (mg/L) |
|---|---|---|---|
| Gross alpha particle activity (excluding radon and uranium) | zero | 15 pCi/L | not a mass unit |
| Beta particles and photon emitters | zero | 4 mrem/year | not a mass unit |
| Combined radium-226 and radium-228 | zero | 5 pCi/L | not a mass unit |
| Uranium | zero | 30 µg/L | 0.030 |

Radon has no federal MCL in force on EPA's NPDWR page; the [uranium and radon in well water guide](/water/guides/uranium-radon-in-well-water/) covers what a lab result for either means.

## What is the PFAS rule as of 2026?

EPA's 2024 PFAS National Primary Drinking Water Regulation is the first federal MCL for these compounds. The table gives the limits as EPA prints them, in parts per trillion (ppt, the same as ng/L), plus the mg/L equivalent.

| PFAS | MCL (ppt) | MCL (mg/L) | Status on EPA's pages, read September 14, 2026 |
|---|---|---|---|
| PFOA | 4.0 | 0.000004 | Enforceable; compliance April 2029, proposed extension to April 2031 |
| PFOS | 4.0 | 0.000004 | Enforceable; compliance April 2029, proposed extension to April 2031 |
| PFHxS | 10 | 0.00001 | Enforceable as written; proposed for rescission |
| PFNA | 10 | 0.00001 | Enforceable as written; proposed for rescission |
| HFPO-DA (GenX) | 10 | 0.00001 | Enforceable as written; proposed for rescission |
| Hazard Index (PFHxS, PFNA, HFPO-DA, PFBS mixtures) | 1 (unitless) | not a mass unit | Proposed for rescission |

EPA's PFAS page gives public water systems three years to complete initial monitoring, by 2027, and the compliance-extension page states MCL compliance is due April 2029 under the rule as written.

EPA's Proposed PFOA and PFOS Compliance Extension Rule would grant systems two additional years, to April 2031; its comment period closed July 20, 2026, after a virtual hearing on July 7, 2026, under docket EPA-HQ-OW-2025-1742. EPA's Proposed PFAS Rescission Rule would withdraw the determinations for PFHxS, PFNA, HFPO-DA and the Hazard Index mixture of those three plus PFBS, and its page was last updated July 23, 2026 with the rule still proposed.

The 4.0 ppt figures for PFOA and PFOS are not part of either proposal. What a home filter can do about a PFAS result is on the [PFAS in tap water guide](/water/guides/pfas-in-tap-water-what-filter/).

## What is the lead action level?

| Trigger | Level | In force |
|---|---|---|
| Current lead action level | 0.015 mg/L (15 ppb), 90th percentile of sampled taps | Now |
| Lead and Copper Rule Improvements (LCRI) action level | 0.010 mg/L (10 ppb), 90th percentile of sampled taps | November 1, 2027 |

EPA's NPDWR page states it directly: beginning on the LCRI compliance date of November 1, 2027, systems must comply with the revised lead action level of 0.010 mg/L. An action level is a system-wide trigger, not a limit on your tap, so one kitchen sample above 0.015 mg/L does not by itself put a utility out of compliance. The [lead guide](/water/guides/lead-in-tap-water-service-line/) covers the service-line check.

## What are the EPA secondary standards?

EPA's National Secondary Drinking Water Standards are non-mandatory. EPA describes them as guides for aesthetic considerations such as taste, color and odor, and does not enforce them.

| Parameter | Secondary standard | OwnerSpec guide |
|---|---|---|
| Aluminum | 0.05 to 0.2 mg/L | none |
| Chloride | 250 mg/L | none |
| Color | 15 color units | [tannins and tea-colored water](/water/guides/tannins-tea-colored-well-water/) |
| Copper | 1.0 mg/L | [blue-green stains and low pH](/water/guides/blue-green-stains-low-ph-well-water/) |
| Corrosivity | Non-corrosive | [blue-green stains and low pH](/water/guides/blue-green-stains-low-ph-well-water/) |
| Fluoride | 2.0 mg/L | [fluoride in tap water](/water/guides/fluoride-in-tap-water-remove/) |
| Foaming agents | 0.5 mg/L | none |
| Iron | 0.3 mg/L | [iron in well water](/water/guides/iron-in-well-water/) |
| Manganese | 0.05 mg/L | [manganese black stains](/water/guides/manganese-black-stains-well-water/) |
| Odor | 3 threshold odor number (TON) | [rotten egg smell](/water/guides/rotten-egg-smell-well-water/) |
| pH | 6.5 to 8.5 | [blue-green stains and low pH](/water/guides/blue-green-stains-low-ph-well-water/) |
| Silver | 0.1 mg/L | none |
| Sulfate | 250 mg/L | none |
| Total dissolved solids (TDS) | 500 mg/L | [RO remineralization](/water/guides/reverse-osmosis-remineralization-do-you-need-it/) |
| Zinc | 5 mg/L | none |

Copper and fluoride appear in both tables with different numbers: the primary copper action level is 1.3 mg/L and the secondary level is 1.0 mg/L; the primary fluoride MCL is 4.0 mg/L and the secondary standard is 2.0 mg/L. The lower figure in each pair is the taste and staining guide, the higher one the enforceable limit. Hardness is on neither list; the [hard water guide](/water/guides/hard-water-white-scale/) covers the gpg scale, and a TDS meter reading guide in this series explains why a 500 mg/L TDS reading says nothing about which contaminant is present.

**Before you buy anything**

Do not buy a filter off this table. A limit tells you what a result means, not what is in your water, and every treatment class on this site is chosen by the contaminant and its concentration. Get a certified lab result first, compare each line against the MCL column, then follow the linked guide for the one that is over. If nothing exceeds an MCL and the complaint is taste, staining or smell, read the secondary table instead.

## What should you do first?

1. Read the unit line on your report and convert to mg/L before comparing: 1 ppm equals 1 mg/L, 1 ppb equals 0.001 mg/L, 1 µg/L equals 0.001 mg/L.
2. Mark every result above its MCL or action level in the primary tables; those are the enforceable ones.
3. Mark every result above a secondary standard separately; those explain taste, stain and odor, not compliance.
4. For lead, note whether the sample was first-draw or flushed; the action level is a 90th-percentile system figure and a single tap result is read differently.
5. Open the linked guide for each marked line to see the treatment class; where none is linked, ask your state drinking water program which local limit applies.

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## Frequently asked questions

### What is the EPA limit for lead in drinking water?

Lead has no MCL. EPA's National Primary Drinking Water Regulations set a Maximum Contaminant Level Goal of zero and a treatment-technique action level of 0.015 mg/L (15 ppb) at the 90th percentile of sampled taps. The same EPA page states that from the Lead and Copper Rule Improvements compliance date of November 1, 2027, systems must meet a revised action level of 0.010 mg/L (10 ppb).

### What is the EPA limit for PFOA and PFOS in drinking water?

EPA's 2024 PFAS National Primary Drinking Water Regulation sets an enforceable MCL of 4.0 parts per trillion, also written as 4.0 ng/L, for PFOA and for PFOS individually, which is 0.000004 mg/L. EPA's PFAS page gives public water systems until 2027 to finish initial monitoring, with MCL compliance due April 2029 under the rule as written.

### Is the EPA PFAS rule still in effect in 2026?

Yes, as written, with two proposals pending. EPA's compliance-extension page proposes moving the PFOA and PFOS deadline from April 2029 to April 2031, and its rescission page proposes withdrawing the limits for PFHxS, PFNA, HFPO-DA and the Hazard Index mixture. Both comment periods closed July 20, 2026, and neither EPA page showed a final rule when read on September 14, 2026.

### What is the EPA nitrate limit for well water?

EPA's National Primary Drinking Water Regulations set the nitrate MCL and MCLG at 10 mg/L measured as nitrogen, and nitrite at 1 mg/L as nitrogen. The limit applies to public water systems only; a private well is not regulated, so a well owner compares a lab result against 10 mg/L as N by choice. A report in mg/L as nitrate uses a different scale, so check the unit line first.

### What is the difference between a primary and a secondary drinking water standard?

A primary standard is an enforceable MCL or treatment technique in EPA's National Primary Drinking Water Regulations, set for a health-based reason. A secondary standard is one of the 15 non-mandatory levels in EPA's National Secondary Drinking Water Standards, which EPA says guide systems on aesthetic effects such as taste, color and odor. Iron at 0.3 mg/L and TDS at 500 mg/L are secondary; arsenic at 0.010 mg/L is primary.


## Sources

- [EPA, National Primary Drinking Water Regulations](https://www.epa.gov/ground-water-and-drinking-water/national-primary-drinking-water-regulations) (government or regulatory source)
- [EPA, Per- and Polyfluoroalkyl Substances (PFAS) National Primary Drinking Water Regulation](https://www.epa.gov/sdwa/and-polyfluoroalkyl-substances-pfas) (government or regulatory source)
- [EPA, Proposed PFOA and PFOS Compliance Extension Rule](https://www.epa.gov/sdwa/proposed-pfoa-and-pfos-compliance-extension-rule) (government or regulatory source)
- [EPA, Proposed PFAS Rescission Rule](https://www.epa.gov/sdwa/proposed-pfas-rescission-rule) (government or regulatory source)
- [EPA, Secondary Drinking Water Standards: Guidance for Nuisance Chemicals](https://www.epa.gov/sdwa/secondary-drinking-water-standards-guidance-nuisance-chemicals) (government or regulatory source)

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Citation: OwnerSpec, "EPA drinking water standards table: every MCL, MCLG, action level and secondary standard a home water test reports against", https://ownerspec.com/water/guides/epa-drinking-water-limits-table/, facts verified 14 September 2026.
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