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

If your lab report already prints an “EPA limit” column beside every result, you can leave now: these are the same numbers, and all this page adds is which of them are enforceable.

Which limits are looked up most?

The ten lines a home report is checked against most often, copied from EPA’s pages on November 3, 2026.

Jump to a group: inorganic chemicals, organic chemicals, microorganisms, disinfectants and byproducts, radionuclides, PFAS, lead action level, secondary standards.

Which limits are enforceable and which are not?

A Maximum Contaminant Level (MCL) is the highest concentration EPA allows from a public water system, and it is enforceable. A Maximum Contaminant Level Goal (MCLG) is the non-enforceable health target, 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 at the 90th percentile of sampled taps. A Maximum Residual Disinfectant Level (MRDL) caps a disinfectant the system adds on purpose. A secondary standard is one of 15 non-mandatory levels set for taste, color and odor.

Every EPA limit applies to public water systems, none to a private well; the well water test panel guide covers which results to order.

What are the EPA MCLs for inorganic chemicals?

Values from EPA’s NPDWR page, in mg/L, the same as parts per million (ppm).

Nitrate and nitrite are stated as nitrogen. A lab reporting “nitrate as NO3” uses a different scale; the nitrate guide shows the conversion.

What are the EPA MCLs for organic chemicals?

EPA’s NPDWR page lists 53 organic chemicals apart from PFAS, mostly solvents and pesticides; acrylamide and epichlorohydrin are treatment techniques on the dose a system may add. Values in mg/L.

A home panel rarely runs this group; it is ordered when a well sits near farmland, a fuel tank or industry.

What are the EPA limits for microorganisms?

Most microbial limits are treatment techniques on the public system. The one a home test returns is total coliforms, which EPA sets as a monthly sample percentage.

A private well reads a positive coliform result against zero; the coliform-positive well guide covers the retest.

What are the EPA limits for disinfectants and disinfection byproducts?

Disinfectants carry an MRDL with a goal (MRDLG) beside it; their byproducts carry an ordinary MCL. Values in mg/L from EPA’s NPDWR page.

A city-water chlorine taste sits under this table, not under a contaminant MCL; the chlorine and chloramine guide covers which filter media takes each one out.

What are the EPA limits for radionuclides?

EPA prints these in the units a lab uses; the table adds mg/L where one exists.

Radon has no federal MCL in force; the uranium and radon guide covers what a lab result for either means.

What is the PFAS rule as of 2026?

EPA’s 2024 PFAS rule is the first federal MCL for these compounds. Limits are in parts per trillion (ppt, the same as ng/L) as EPA prints them, plus the mg/L equivalent.

EPA’s PFAS page gives systems until 2027 to complete initial monitoring, 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 two more 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 limits for PFHxS, PFNA, HFPO-DA and the Hazard Index mixture of those three plus PFBS. Both pages were last updated October 8, 2026 with the rules still proposed.

The 4.0 ppt figures for PFOA and PFOS are not part of either proposal; the PFAS in tap water guide covers what a home filter can do.

What is the lead action level?

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, so one kitchen sample above 0.015 mg/L does not by itself put a utility out of compliance. The lead guide covers the service-line check.

What are the EPA secondary standards?

EPA describes its 15 secondary standards as non-mandatory guides for taste, color and odor, with one exception on the same page: a community system over the fluoride secondary standard of 2.0 mg/L must notify the people it serves within 12 months.

Copper and fluoride appear in both tables: copper 1.3 mg/L primary against 1.0 mg/L secondary, fluoride 4.0 mg/L primary against 2.0 mg/L secondary. The lower figure is the taste and staining guide, the higher one the enforceable limit. Hardness is on neither list; the hard water guide covers the gpg scale, and the TDS meter guide explains why a 500 mg/L TDS reading says nothing about which contaminant is present.

What should you do first?

1. Convert the report to mg/L before comparing: 1 ppm equals 1 mg/L, 1 ppb and 1 µg/L each equal 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; a single tap result is not the 90th-percentile figure.
5. Open the linked guide for each marked line; where none is linked, ask your state drinking water program.

Frequently asked questions

Sources

1. EPA, National Primary Drinking Water Regulations (government or regulatory source)
2. EPA, Per- and Polyfluoroalkyl Substances (PFAS) National Primary Drinking Water Regulation (government or regulatory source)
3. EPA, Proposed PFOA and PFOS Compliance Extension Rule (government or regulatory source)
4. EPA, Proposed PFAS Rescission Rule (government or regulatory source)
5. EPA, Secondary Drinking Water Standards: Guidance for Nuisance Chemicals (government or regulatory source)

Found a number that does not match its source? Tell us which page and which figure, and it gets checked against the document and fixed.