Montana DPHHS
Montana drinking water lab licensure, DPHHS and ARM 37.12.3.
Who licenses labs that analyze Montana public water supplies, which EPA manual the rules adopt, how out-of-state labs qualify, and where calibration sits in the rules.
At a glance
How drinking water lab licensure works in Montana.
Montana is not a NELAP state. The Department of Public Health and Human Services licenses labs that analyze water from public water supplies, under its own rules and the EPA drinking water certification manual.
Drinking water lab certification
- Program
- Water Laboratory Certification Program, Montana Department of Public Health and Human Services. The rules call it licensure, and the department’s environmental laboratory is responsible for licensing labs performing drinking water analyses (ARM 37.12.301).
- Legal basis
- Section 75-6-106, MCA, and the Laboratories rules in ARM 37.12.3. The Department of Environmental Quality may not accept required public water supply analyses unless they come from the DPHHS laboratory or a lab DPHHS has licensed.
- Who needs it
- Labs that analyze water from public water supplies, before DEQ will accept the analyses for public water supply compliance (ARM 37.12.304).
- License categories
- Microbiology and chemical testing are separate categories, each with its own application, inspection and license. A license covers only the analytes and methods the department approves.
- Reference manual
- EPA Manual for the Certification of Laboratories Analyzing Drinking Water, 5th edition, January 2005 (EPA 815-R-05-004). Chapter IV is incorporated for chemistry labs (ARM 37.12.345).
- Out-of-state labs
- Reciprocal licensure under ARM 37.12.313 for labs approved by EPA or by a home state with an EPA-approved program. A separate route covers NELAP-accredited labs using EPA-approved drinking water methods.
- NELAP status
- Not a NELAP accreditation body as of October 2026. Montana licenses labs under its own rules.
The accreditation cycle
From application to renewal.
The steps below summarize ARM 37.12.3 for in-state labs. Your license and DPHHS correspondence govern the specifics for your lab.
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Apply by category
Apply separately for chemistry, microbiology or both, listing the analytes and methods the license should cover.
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Three-year license
A license is valid for three years while the lab meets the rules, completes the annual questionnaires and pays the annual fees (ARM 37.12.311).
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Performance evaluation samples
Chemistry labs analyze at least two PE samples for each analyte or interdependent analyte group and each method each year. Microbiology labs must successfully analyze at least two per analyte and method each year.
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On-site inspection
At least one on-site inspection by the DPHHS environmental laboratory during the three-year term of the license (ARM 37.12.306).
Initial calibration
What auditors check in your initial calibrations.
Montana’s rules put calibration inside the lab’s quality assurance plan and incorporate the EPA drinking water certification manual, so the drinking water methods you are licensed for supply the acceptance criteria.
A range that brackets what you report
The lowest standard should sit at or below your reporting limit and the highest at or above the top concentration you report. Results outside the calibrated range need to be qualified.
Error at the low end, not r² alone
A correlation coefficient of 0.999 can still hide a low standard that back-calculates 30 percent off. Auditors look at relative error, especially at the lowest levels.
Records that rebuild the curve
Raw responses, the model and weighting used, any excluded points with the reason, and the verification that followed. An auditor should be able to reconstruct every initial calibration from the record.
Calibration written into the QA plan
ARM 37.12.336 requires every licensed lab’s quality assurance plan to cover equipment operation and calibration. Chemistry labs must also include calibration procedures, instrument performance checks and control charts, and QA records are kept for five years.
Source: ARM 37.12.336
In a January 2023 letter to certified water testing labs, DPHHS stated that drinking water method protocols “are not guidelines” and that DEQ will not accept results for compliance that do not follow them.
Self-check
Are your initial calibrations ready for a Montana assessment?
Tick what your lab could show an auditor today. Nothing you select is saved or sent anywhere.
6Checks to work through
Select each item your lab could show an auditor today.
A self-assessment to help you prepare, not a compliance determination.
Montana specifics
Montana licenses drinking water labs to a 2005 EPA manual.
Montana’s program is built around public water supplies. Section 75-6-106, MCA, bars DEQ from accepting required public water supply analyses unless a DPHHS licensed lab or the DPHHS laboratory produced them, and ARM 37.12.304 ties licensure to analyses of water from public water supplies.
The rules lean on the EPA drinking water certification manual, 5th edition, January 2005, and on the lab’s own quality assurance plan. That plan must address equipment operation and calibration, and chemistry labs must document calibration procedures and instrument performance checks. An auditor reads your calibration records against that plan and the methods you are licensed for.
The last substantive amendment we found was MAR Notice No. 37-1015, published in March 2023. It updated the 40 CFR 136 references for the initial demonstration of capability and the method detection limit to the versions amended August 28, 2017, and corrected the links to the EPA manual, whose January 2005 edition did not change.
How WLTR helps
Calibration evidence ready for a Montana inspection.
WLTR independently reviews the calibration your instrument software produced. Your analyst still makes the final call. What changes is that the evidence is complete, consistent across analysts, and ready before the auditor asks for it.
- Each analyte reviewed one at a time in the instrument software.
- The model and weighting are whatever the batch was processed with.
- r² is the number most people look at, even though it does not measure error at the low end.
- QA signs off without an independent check on the curve.
- Every analyte and every candidate model side by side in the Calibration Intelligence dashboard.
- Diagnostics run automatically and the best fit curve is identified, with the reasons recorded.
- Relative error at every level, including the lowest standard, shown on one screen.
- A traceable record your QA manager can review, sign and hand to a state auditor.
See how your own ICAL data looks when every analyte and model is laid out for review.
Questions
Montana accreditation FAQs
Is Montana a NELAP state?
No. Montana is not on TNI’s list of NELAP accreditation bodies. DPHHS licenses drinking water labs under ARM 37.12.3, and NELAP-accredited labs can apply for a Montana license on that basis under ARM 37.12.313.
Who licenses drinking water labs in Montana?
The Montana Department of Public Health and Human Services, through its environmental laboratory, under section 75-6-106, MCA, and ARM 37.12.3.
Can an out-of-state lab analyze Montana public water supply samples?
Yes, with a reciprocal license under ARM 37.12.313. The lab must be approved by EPA or by a home state with an EPA-approved program, meet requirements no less stringent than Montana’s, and pass PE audits reported directly to DPHHS.
How long does a Montana lab license last?
Three years for in-state labs (ARM 37.12.311). Labs must pass at least one on-site inspection during the term and analyze at least two PE samples per analyte and method each year. A reciprocal license runs for the same period as the home approval.
Does Montana have its own calibration rule?
ARM 37.12.336 requires the quality assurance plan to cover equipment operation and calibration, and chemistry labs must include calibration procedures and instrument performance checks. Method criteria come from the EPA drinking water methods.
Sources
Primary sources for this page.
- Montana DPHHS, Water Laboratory Certification Program (opens in a new tab)
- MCA 75-6-106, laboratory license required (opens in a new tab)
- ARM 37.12.304, licensure coverage (Justia copy) (opens in a new tab)
- ARM 37.12.306, standards, inspections and tests (Justia copy) (opens in a new tab)
- ARM 37.12.313, reciprocity (Justia copy) (opens in a new tab)
- ARM 37.12.336, quality assurance (Justia copy) (opens in a new tab)
- MAR Notice No. 37-1015, notice of amendment (opens in a new tab)
- TNI, NELAP recognized accreditation bodies (opens in a new tab)
- Montana DPHHS, letter to certified water testing laboratories, January 2023 (opens in a new tab)
- MAR Notice No. 37-1015, proposal notice (opens in a new tab)
This page summarizes public program information to help labs prepare. Requirements change, and the agency’s current rules and guidance always take precedence. WLTR is not affiliated with or endorsed by the Montana Department of Public Health and Human Services. Spot something out of date? Tell us at admin@wltr.tech.
Before your next assessment
See your Montana ICALs the way an auditor will.
Bring a recent initial calibration. We will walk you through every analyte and candidate model in the Calibration Intelligence dashboard, the best fit, and the record your QA manager would sign.
Request a demoHow the methodology works
Running environmental methods? See how WLTR works for environmental testing labs and water and wastewater utility labs.