Nobody tests a private well for you. EPA's private-well page says it plainly: "Private well owners are responsible for delivering safe drinking water to their households." So how easy is it, in practice, to get a well tested by a certified lab? We scored the state and territory lists we track on five things a well owner runs into: whether a certified lab sits in their county, how many in-state labs there are for the number of well users, whether the state says which labs take samples from homeowners, whether there is a free testing program, and whether state law requires a test when a home is sold. Our data covers 45 lists: every state except Arkansas, Delaware, North Dakota, New Hampshire, New Jersey and Utah, plus Puerto Rico. The District of Columbia is not covered.
- In the 42 ranked states and territories, 12,823,022 of 37,423,963 private-well users (34%) live in a county with no in-state certified lab on their state's list.
- The typical state has 0.53 in-state certified labs per 10,000 private-well users (the median across ranked states).
- Of the 45 lists we track, only 6 states run a statewide free or subsidized testing program we could find in their official pages, and only 2 of those are open to well owners without a restriction on who or what is tested.
- Of the 45 lists we track, only 3 states, Maryland, Oregon, Rhode Island, require a water test by law when a home with a well is sold (in Maryland the buyer can waive it in writing). New Jersey, which is not in our data, also requires one under its Private Well Testing Act.
- On our index, California (64.9), Wisconsin (64.7) and Oregon (63.2) score highest; the first two are almost tied. The order at the top changes if you change the weights. The bottom barely changes: South Dakota, Vermont, Nebraska, Mississippi and Georgia are the bottom five under every weighting we tried, and three of them are flagged lists.
The index is one transparent weighting, not a verdict on any state's health department. Every component is shown, and the full by-state table can be requested, so the states can be re-ranked under other weights.
A third of well users have no certified lab in their county
Most tests can be mailed, but bacteria samples have to reach the lab quickly, often within a day or so of collection (our testing-deserts study sets out the holding-time rules). A lab in your own county makes that far easier.
Across the 42 ranked lists, 24,600,941 private-well users (66%) live in a county where at least one lab on their own state's list has an in-state address. The other 12,823,022 (34%) do not. That is in line with what the testing-deserts study found in the nine states it covered, with a slightly different rule: that study counted any listed lab located in the county, whichever state listed it, while this index counts only in-state labs on the state's own list.
Show the numbers
| Item | Value | Note |
|---|---|---|
| Massachusetts | 92.4 percent of the state's private-well users (USGS 2015) | |
| North Carolina | 91.8 percent of the state's private-well users (USGS 2015) | |
| California | 89.9 percent of the state's private-well users (USGS 2015) | |
| Washington | 88 percent of the state's private-well users (USGS 2015) | |
| Michigan | 87.7 percent of the state's private-well users (USGS 2015) | |
| Maryland | 85.7 percent of the state's private-well users (USGS 2015) | |
| Wisconsin | 85 percent of the state's private-well users (USGS 2015) | |
| Rhode Island | 84.9 percent of the state's private-well users (USGS 2015) | |
| Florida | 82.6 percent of the state's private-well users (USGS 2015) | |
| Pennsylvania | 82.4 percent of the state's private-well users (USGS 2015) | |
| Connecticut | 75 percent of the state's private-well users (USGS 2015) | |
| Nevada | 75 percent of the state's private-well users (USGS 2015) | |
| Oregon | 75 percent of the state's private-well users (USGS 2015) | |
| Maine | 72.3 percent of the state's private-well users (USGS 2015) | |
| Wyoming | 71.5 percent of the state's private-well users (USGS 2015) | |
| Tennessee | 71.1 percent of the state's private-well users (USGS 2015) | |
| Illinois | 70.2 percent of the state's private-well users (USGS 2015) | |
| Arizona | 60.2 percent of the state's private-well users (USGS 2015) | |
| Virginia | 59.7 percent of the state's private-well users (USGS 2015) | |
| New Mexico | 59.3 percent of the state's private-well users (USGS 2015) | |
| Colorado | 57.9 percent of the state's private-well users (USGS 2015) | |
| Texas | 54.7 percent of the state's private-well users (USGS 2015) | |
| Indiana | 54.6 percent of the state's private-well users (USGS 2015) | |
| Montana | 53.5 percent of the state's private-well users (USGS 2015) | |
| South Carolina | 51.8 percent of the state's private-well users (USGS 2015) | |
| Ohio | 46.1 percent of the state's private-well users (USGS 2015) | |
| Louisiana | 45.1 percent of the state's private-well users (USGS 2015) | |
| Missouri | 41.9 percent of the state's private-well users (USGS 2015) | |
| Iowa | 40 percent of the state's private-well users (USGS 2015) | |
| Minnesota | 39.6 percent of the state's private-well users (USGS 2015) | |
| Alabama | 36.1 percent of the state's private-well users (USGS 2015) | |
| Idaho | 34.1 percent of the state's private-well users (USGS 2015) | |
| Oklahoma | 34 percent of the state's private-well users (USGS 2015) | |
| Vermont | 29.7 percent of the state's private-well users (USGS 2015) | |
| West Virginia | 27.7 percent of the state's private-well users (USGS 2015) | |
| Kansas | 17.2 percent of the state's private-well users (USGS 2015) | |
| Puerto Rico | 13.1 percent of the state's private-well users (USGS 2015) | |
| Mississippi | 10.7 percent of the state's private-well users (USGS 2015) | |
| South Dakota | 10 percent of the state's private-well users (USGS 2015) | |
| Georgia | 7 percent of the state's private-well users (USGS 2015) | |
| Nebraska | 4.7 percent of the state's private-well users (USGS 2015) | |
| Hawaii | 0 percent of the state's private-well users (USGS 2015) |
Not ranked: New York, Kentucky and Alaska (partial lists). Stale or partial lists flagged in the method. Hawaii's 0% is an artifact: most of its in-state labs print no address, so they cannot be placed in a county. Source: WaterListed analysis of official state lab lists, USGS 2015 county water use and state health/environment pages (method on this page), accessed 2026-11-04.
Among clean lists, coverage is lowest in South Dakota (10%), Kansas (17%), West Virginia (28%), Vermont (30%) and Oklahoma (34%).
Coverage and lab counts can tell different stories. Kansas has one of the higher lab densities in the table (1.21 per 10,000 well users) but only 17% coverage, because its listed in-state labs sit in a few counties. Connecticut has few labs for its well population (0.20 per 10,000) but 75% coverage, because it is a small state with few counties, so a handful of labs reaches most well users. That is why the index uses both measures.
How many labs there are for the number of well users
The second measure is in-state labs on each state's list per 10,000 private-well users (USGS 2015). The median across ranked states is 0.53 labs per 10,000 well users.
Show the numbers
| Item | Value | Note |
|---|---|---|
| Colorado | 2.3 labs per 10,000 private-well users (USGS 2015) | |
| Tennessee | 2.07 labs per 10,000 private-well users (USGS 2015) | |
| California | 1.84 labs per 10,000 private-well users (USGS 2015) | |
| Hawaii | 1.6 labs per 10,000 private-well users (USGS 2015) | |
| Kansas | 1.21 labs per 10,000 private-well users (USGS 2015) | |
| Arizona | 1.05 labs per 10,000 private-well users (USGS 2015) | |
| Wyoming | 1.01 labs per 10,000 private-well users (USGS 2015) | |
| Nevada | 0.99 labs per 10,000 private-well users (USGS 2015) | |
| Wisconsin | 0.84 labs per 10,000 private-well users (USGS 2015) | |
| Missouri | 0.83 labs per 10,000 private-well users (USGS 2015) | |
| North Carolina | 0.83 labs per 10,000 private-well users (USGS 2015) | |
| New Mexico | 0.79 labs per 10,000 private-well users (USGS 2015) | |
| Iowa | 0.77 labs per 10,000 private-well users (USGS 2015) | |
| Texas | 0.71 labs per 10,000 private-well users (USGS 2015) | |
| Michigan | 0.67 labs per 10,000 private-well users (USGS 2015) | |
| Florida | 0.59 labs per 10,000 private-well users (USGS 2015) | |
| West Virginia | 0.59 labs per 10,000 private-well users (USGS 2015) | |
| Alabama | 0.57 labs per 10,000 private-well users (USGS 2015) | |
| Illinois | 0.55 labs per 10,000 private-well users (USGS 2015) | |
| Oregon | 0.54 labs per 10,000 private-well users (USGS 2015) | |
| Virginia | 0.53 labs per 10,000 private-well users (USGS 2015) | |
| Montana | 0.49 labs per 10,000 private-well users (USGS 2015) | |
| Oklahoma | 0.45 labs per 10,000 private-well users (USGS 2015) | |
| Washington | 0.44 labs per 10,000 private-well users (USGS 2015) | |
| Louisiana | 0.43 labs per 10,000 private-well users (USGS 2015) | |
| Massachusetts | 0.39 labs per 10,000 private-well users (USGS 2015) | |
| Rhode Island | 0.35 labs per 10,000 private-well users (USGS 2015) | |
| Pennsylvania | 0.32 labs per 10,000 private-well users (USGS 2015) | |
| South Dakota | 0.31 labs per 10,000 private-well users (USGS 2015) | |
| Nebraska | 0.29 labs per 10,000 private-well users (USGS 2015) | |
| Indiana | 0.28 labs per 10,000 private-well users (USGS 2015) | |
| Idaho | 0.28 labs per 10,000 private-well users (USGS 2015) | |
| Ohio | 0.27 labs per 10,000 private-well users (USGS 2015) | |
| Maryland | 0.27 labs per 10,000 private-well users (USGS 2015) | |
| Vermont | 0.25 labs per 10,000 private-well users (USGS 2015) | |
| Minnesota | 0.21 labs per 10,000 private-well users (USGS 2015) | |
| South Carolina | 0.21 labs per 10,000 private-well users (USGS 2015) | |
| Connecticut | 0.2 labs per 10,000 private-well users (USGS 2015) | |
| Maine | 0.18 labs per 10,000 private-well users (USGS 2015) | |
| Mississippi | 0.12 labs per 10,000 private-well users (USGS 2015) | |
| Georgia | 0.1 labs per 10,000 private-well users (USGS 2015) |
Not ranked: New York, Kentucky and Alaska (partial lists). Stale or partial lists flagged in the method. Puerto Rico is left off this chart: with about 4,700 private-well users its ratio is not comparable (it is in the CSV). Source: WaterListed analysis of official state lab lists, USGS 2015 county water use and state health/environment pages (method on this page), accessed 2026-11-04.
Among clean lists with at least 100,000 well users, the highest densities are in Colorado (2.30), Tennessee (2.07), California (1.84), Kansas (1.21) and Arizona (1.05). The lowest are Maine (0.18), Connecticut (0.20), South Carolina (0.21), Minnesota (0.21) and Vermont (0.25).
Puerto Rico is left off the chart. Its raw figure, 14.87, would top it, but that figure means little. USGS puts Puerto Rico's private-well population at only 4,708, so one lab more or less moves the rate a lot. Hawaii (1.60, 56,296 well users) has the same small-denominator problem.
A high count of labs does not mean every lab takes a sample from a household. Some certified labs serve utilities or their own water system only. Out-of-state mail-in labs are left out of this measure, because the index is about labs close enough for a time-limited bacteria sample; we also keep the all-labs rate for each state in our by-state table.
How the index works
The index runs from 0 to 100. Higher means it is easier for a well owner to get a certified test. It combines five components with fixed weights:
| Component | What it measures | How it is scored | Weight |
|---|---|---|---|
| Coverage | Share of the state's private-well users (USGS 2015) living in a county with at least one in-state lab on the state's own list | The percentage itself. Used only where at least 80% of in-state labs could be placed in a county | 30 |
| Lab density | In-state labs on the state's list per 10,000 private-well users | Percentile rank among ranked states (0 lowest, 100 highest), because the raw values are very skewed | 25 |
| Homeowner marks | Share of listed labs the state itself marks as taking homeowner or public samples | The percentage itself. Used only in the 7 states whose list marks every lab yes or no | 15 |
| Free program | A free or subsidized testing program in the state's official pages | Statewide 100; statewide but restricted (eligibility, PFAS only or screening only) 50; named areas only 25; none found 0 | 20 |
| Home-sale law | State law requires a water test when a home with a well is sold | Yes 100, no 0 | 10 |
When a component is missing for a state, it is left out and the other weights are scaled back up to 100. The index is the weighted sum of the components a state has, divided by the sum of their weights; our by-state table records which went in for each state. Missing homeowner marks are never scored as zero: a lab whose homeowner status the list does not state is not treated as a lab that refuses homeowner samples. (This applies to homeowner marks only: a free program "none found" in the pages we read scores 0, as does "no" for the home-sale law.) That is why California, Louisiana, Vermont, whose lists mark some labs and leave others unmarked, get no homeowner component.
The state-lab price of a coliform test is recorded in our by-state table but not scored. Only 12 states have a standalone state-lab coliform price in our fact-checked pages, and finding no price in those pages is not evidence that a state has no low-cost lab.
What counts as a lab. One lab is one WaterListed lab page; a business listed more than once counts once. "In-state" means the lab's address is in the state whose list names it. Lab locations come from the address on the list (ZIP code, or town where a list gives no ZIP). The data covers 2,295 labs from 3,359 listings on 45 state and territory lists, in the version of our data dated 2026-11-07.
Which states are ranked. 42 of the 45 lists are ranked. New York, Kentucky, Alaska are computed but not ranked, because the lists we hold for them are partial: New York's covers only labs in its PFAS rebate program, Kentucky's only PFAS-certified labs, and Alaska's only its microbiology page. Lists that are stale or partial in other ways are ranked but flagged, and the headline "clean" figures leave them out.
The top changes with the weights; the bottom barely does
We tested two other weightings on the same data. With equal weights for all five components, the top five become Oregon, Rhode Island, Wisconsin, Colorado and Iowa: Rhode Island rises because of its home-sale law. With the three lab components only, weighted equally (coverage, density and homeowner marks), the top five become Puerto Rico, California, Hawaii, Tennessee and North Carolina. Puerto Rico and Hawaii jump there because their scores then rest on lab density alone, the small-denominator measure described above.
The bottom is much more stable. South Dakota, Vermont, Nebraska, Mississippi and Georgia are the bottom five under all three weightings, though their order shifts. Three of them (Nebraska, Mississippi and Georgia) are flagged lists, so part of their low score may come from gaps in the list. If you care about one component more than the others, the by-state table with each state's component scores is available on request (see Getting the data below).
State by state: the index
Show the numbers
| Item | Value | Note |
|---|---|---|
| California | 64.9 index points | |
| Wisconsin | 64.7 index points | |
| Oregon | 63.2 index points | |
| Colorado | 60.4 index points | |
| Iowa | 57.7 index points | |
| Washington | 56.8 index points | |
| North Carolina | 53.9 index points | |
| New Mexico | 53.5 index points | |
| Tennessee | 53.1 index points | |
| Rhode Island | 51.8 index points | |
| Nevada | 50.1 index points | |
| Wyoming | 49.6 index points | |
| Michigan | 49.6 index points | |
| Florida | 47.1 index points | |
| Maryland | 47 index points | |
| Arizona | 46.4 index points | |
| Massachusetts | 46 index points | |
| Puerto Rico | 45.5 index points | |
| Idaho | 42 index points | |
| Hawaii | 41 index points | |
| Illinois | 40.5 index points | |
| Texas | 38.7 index points | |
| Pennsylvania | 38.4 index points | |
| Missouri | 37 index points | |
| Connecticut | 35.8 index points | |
| Virginia | 35.4 index points | |
| Oklahoma | 34.7 index points | |
| South Carolina | 32.9 index points | |
| Montana | 32.5 index points | |
| Kansas | 31.9 index points | |
| Minnesota | 29.9 index points | |
| Alabama | 29.2 index points | |
| Louisiana | 27.4 index points | |
| West Virginia | 27 index points | |
| Maine | 26.9 index points | |
| Indiana | 26.4 index points | |
| Ohio | 22 index points | |
| Vermont | 14.8 index points | |
| South Dakota | 12.1 index points | |
| Nebraska | 9.5 index points | |
| Mississippi | 4.5 index points | |
| Georgia | 2.5 index points |
Not ranked: New York, Kentucky and Alaska (partial lists). Stale or partial lists flagged in the method. Weights: coverage 30, in-state lab density 25, homeowner marks 15, free program 20, home-sale law 10. Source: WaterListed analysis of official state lab lists, USGS 2015 county water use and state health/environment pages (method on this page), accessed 2026-11-04.
The top five are California (64.9), Wisconsin (64.7), Oregon (63.2), Colorado (60.4) and Iowa (57.7). All five have clean lists. They get there by different routes. California combines high lab density (1.84 per 10,000 well users) with 90% coverage and regional free programs; its homeowner component is left out because many labs on its list carry no mark. Wisconsin has many in-state labs on its list, which on this site is its coliform-bacteria labs, and 85% coverage, plus a PFAS testing program for eligible well owners. Oregon has fewer in-state labs per well user (0.54) but marks most of its labs for homeowner samples (86%) and is one of the 3 home-sale-law states in our data. Colorado has the highest lab density among clean lists with at least 100,000 well users. Iowa is one of the two states with an unrestricted statewide free program.
Among clean lists, the lowest scores are South Dakota (12), Vermont (15), Ohio (22), Indiana (26) and Maine (27). The raw bottom three, Georgia (2), Mississippi (4) and Nebraska (10), are all flagged lists, so part of their low score may reflect what is missing from the list rather than missing labs.
A low score is not a judgment on a state's labs or staff. It means a well owner there may have to plan more: a lab outside the county, a courier or a mail-in kit.
The full table follows. An asterisk marks a stale or partial list. Coverage for Hawaii and Puerto Rico is shown as computed but is not scored.
| State | Rank | Index | Labs on list (in-state) | Private-well users (USGS 2015) | In-state labs per 10,000 well users | Well users in a county with an in-state listed lab | Labs marked for homeowner samples |
|---|---|---|---|---|---|---|---|
| California | 1 | 65 | 303 (264) | 1,435,510 | 1.84 | 90% | at least 44% (some labs not stated) |
| Wisconsin | 2 | 65 | 136 (135) | 1,598,065 | 0.84 | 85% | not stated per lab |
| Oregon | 3 | 63 | 91 (34) | 631,538 | 0.54 | 75% | 86% |
| Colorado | 4 | 60 | 94 (66) | 286,474 | 2.30 | 58% | 57% |
| Iowa | 5 | 58 | 58 (38) | 494,022 | 0.77 | 40% | not stated per lab |
| Washington | 6 | 57 | 84 (45) | 1,023,853 | 0.44 | 88% | 100% |
| North Carolina | 7 | 54 | 238 (199) | 2,407,661 | 0.83 | 92% | not stated per lab |
| New Mexico | 8 | 53 | 44 (23) | 292,165 | 0.79 | 59% | not stated per lab |
| Tennessee | 9 | 53 | 149 (123) | 594,482 | 2.07 | 71% | not stated per lab |
| Rhode Island | 10 | 52 | 43 (4) | 112,853 | 0.35 | 85% | not stated per lab |
| Nevada | 11 | 50 | 57 (19) | 192,557 | 0.99 | 75% | not stated per lab |
| Wyoming* | 12 | 50 | 12 (12) | 119,066 | 1.01 | 72% | not stated per lab |
| Michigan* | 13 | 50 | 212 (173) | 2,597,314 | 0.67 | 88% | not stated per lab |
| Florida | 14 | 47 | 222 (146) | 2,460,295 | 0.59 | 83% | not stated per lab |
| Maryland | 15 | 47 | 92 (38) | 1,423,948 | 0.27 | 86% | not stated per lab |
| Arizona | 16 | 46 | 51 (23) | 218,170 | 1.05 | 60% | not stated per lab |
| Massachusetts* | 17 | 46 | 36 (24) | 615,948 | 0.39 | 92% | 61% |
| Puerto Rico* | 18 | 45 | 12 (7) | 4,708 | 14.87 | 13% (not scored) | not stated per lab |
| Idaho | 19 | 42 | 33 (11) | 396,215 | 0.28 | 34% | not stated per lab |
| Hawaii | 20 | 41 | 19 (9) | 56,296 | 1.60 | 0% (not scored) | not stated per lab |
| Illinois | 21 | 41 | 96 (63) | 1,151,113 | 0.55 | 70% | not stated per lab |
| Texas | 22 | 39 | 143 (93) | 1,315,073 | 0.71 | 55% | not stated per lab |
| Pennsylvania* | 23 | 38 | 171 (111) | 3,470,761 | 0.32 | 82% | not stated per lab |
| Missouri | 24 | 37 | 89 (68) | 821,343 | 0.83 | 42% | not stated per lab |
| Connecticut | 25 | 36 | 17 (17) | 861,472 | 0.20 | 75% | 76% |
| Virginia | 26 | 35 | 146 (82) | 1,558,115 | 0.53 | 60% | not stated per lab |
| Oklahoma | 27 | 35 | 31 (16) | 356,860 | 0.45 | 34% | 90% |
| South Carolina | 28 | 33 | 48 (25) | 1,182,721 | 0.21 | 52% | not stated per lab |
| Montana | 29 | 33 | 36 (15) | 304,630 | 0.49 | 54% | not stated per lab |
| Kansas | 30 | 32 | 47 (18) | 149,282 | 1.21 | 17% | not stated per lab |
| Minnesota | 31 | 30 | 25 (25) | 1,176,917 | 0.21 | 40% | 100% |
| Alabama* | 32 | 29 | 64 (31) | 539,394 | 0.57 | 36% | not stated per lab |
| Louisiana | 33 | 27 | 49 (21) | 491,582 | 0.43 | 45% | at least 65% (some labs not stated) |
| West Virginia | 34 | 27 | 50 (23) | 391,591 | 0.59 | 28% | not stated per lab |
| Maine | 35 | 27 | 12 (12) | 660,497 | 0.18 | 72% | not stated per lab |
| Indiana | 36 | 26 | 75 (47) | 1,677,339 | 0.28 | 55% | not stated per lab |
| Ohio | 37 | 22 | 75 (50) | 1,861,023 | 0.27 | 46% | not stated per lab |
| Vermont | 38 | 15 | 46 (6) | 243,796 | 0.25 | 30% | at least 57% (some labs not stated) |
| South Dakota | 39 | 12 | 16 (4) | 128,711 | 0.31 | 10% | not stated per lab |
| Nebraska* | 40 | 10 | 5 (5) | 171,440 | 0.29 | 5% | not stated per lab |
| Mississippi* | 41 | 4 | 5 (5) | 434,766 | 0.12 | 11% | not stated per lab |
| Georgia* | 42 | 2 | 43 (15) | 1,514,397 | 0.10 | 7% | not stated per lab |
| Alaska* | not ranked | not ranked | 26 (24) | 188,794 | 1.27 | 94% | not stated per lab |
| Kentucky* | not ranked | not ranked | 14 (0) | 440,663 | 0.00 | 0% | not stated per lab |
| New York* | not ranked | not ranked | 39 (7) | 2,499,435 | 0.03 | 17% | not stated per lab |
Free testing programs: statewide in only a handful of states
We looked for free or subsidized testing in the official state pages behind our fact-checked state guidance. Of the 45 lists we track, only 6 states have a statewide program, and only 2 of them, Iowa and Idaho, are open to well owners without a restriction on eligibility or on the tests covered. 4 more states have programs for named areas only. In the other 35 we found none in the pages we read.
| State | Category in the index | What the official page describes |
|---|---|---|
| Iowa | Statewide | Free testing through county environmental health offices under the Private Well Grants program; Iowa DNR says nearly all counties take part. Standard tests: nitrate, bacteria, manganese and arsenic. A county specialist collects the sample. |
| Idaho | Statewide | A free mailed kit from the Department of Health and Welfare while funding lasts, covering nitrate, arsenic, lead, uranium and other inorganics. No bacteria test. |
| Wisconsin | Statewide, restricted | Free PFAS kit and analysis for eligible well owners (DNR program). |
| Colorado | Statewide, restricted | Free PFAS testing for any private-well owner while supplies last (CDPHE PFAS TAP). |
| New Mexico | Statewide, restricted | Free screening for nitrate, iron and fluoride at NMED field offices; NMED says it does not replace testing by a certified lab. NMED also runs free rural Water Fairs. |
| South Carolina | Statewide, restricted | Well owners over age 65 or on public assistance can get one coliform test and one metals and minerals analysis a year from the state lab. |
| Oregon | Named areas | Free test for households in the Lower Umatilla Basin Groundwater Management Area (Morrow and Umatilla counties). |
| California | Named areas | Domestic well programs funded or regulated by the State Water Board in parts of several counties; services and eligibility differ. |
| Washington | Named areas | Free nitrate and coliform testing in the Lower Yakima Valley and Western Benton County. |
| New York (not ranked) | Named areas | A PFAS testing pilot in Dutchess, Orange, Putnam, Suffolk, Ulster and Westchester counties. |
Counties, cities and universities also run testing days and subsidized kits that are not on state pages, so ask your county health department. Our guide to free well water testing explains where to look, and the guide to well water testing cost covers what a test costs when it is not free.
Home-sale testing laws: Oregon, Rhode Island and Maryland in our data
A required test at sale means that a home with a well gets tested when it changes hands, unless, in Maryland, the buyer waives the test in writing. Of the 45 lists we track, only 3 states have one. Oregon's Domestic Well Testing Act (ORS 448.271) requires the seller to have the well tested for arsenic, nitrate and total coliform bacteria by an accredited lab, and Oregon's rules say the test cannot be waived. Rhode Island's private drinking water regulation (216-RICR-50-05-2, section 2.12) requires testing before a property with a well is sold or transferred. Maryland's Real Property § 10-713, in force since October 1, 2024, requires the sale contract to make a well-water test a condition of the sale; the buyer arranges it and may waive it in writing, and settlement waits until both sides have reviewed the results. We first missed Maryland's law and added it on November 10, 2026, which raised Maryland's index score. Connecticut requires disclosure of testing information to the buyer, not a test, so it scores zero on this component.
New Jersey is not in our data because we do not yet hold a live New Jersey lab list, but it has a home-sale testing law too. A New Jersey DEP summary of its rules says: "The PWTA Rules require testing at the time of a real estate transaction, or every five years for rental properties, and notification to potential buyers and tenants." So this is not a 50-state count.
In most other states a test at sale depends on the lender, the buyer or a local rule. Our guides to well inspections and to FHA, VA and USDA well water test requirements cover those cases.
Which labs take samples from homeowners
A certified lab will not always take your sample. Only 7 states mark every lab on their list yes or no for homeowner or public samples, so only those states get the homeowner component. In 3 more, California, Louisiana, Vermont, the list marks some labs and leaves the rest unmarked, so the share below is a floor. In 14 states a separate state page names a few labs, which again gives only a floor, and 21 states do not say per lab at all.
| State | Share of listed labs marked | What the mark says |
|---|---|---|
| Washington | 100% | Accepts commercial/public samples |
| Minnesota | 100% | MDH list of labs accepting samples from private well users |
| Oklahoma | 90% | Commercial sample column |
| Oregon | 86% | Accepts public samples (OHA: "can accept samples from anyone") |
| Connecticut | 76% | "Private Well Testing" column |
| Louisiana | at least 65% (some labs not stated) | Accepts commercial samples (chemistry list only) |
| Massachusetts | 61% | "Offers services to residential customers?" |
| Colorado | 57% | Accepts outside samples |
| Vermont | at least 57% (some labs not stated) | Green highlighting for labs accepting private samples |
| California | at least 44% (some labs not stated) | Lab type "Commercial" |
These marks are not like for like. Washington, California, Louisiana, Oklahoma and Colorado mark commercial, public or outside samples, which is broader than "household samples". Vermont marks by highlighting, so an unhighlighted lab is "not stated" rather than "no". The finder shows each lab's flag where a state publishes one.
State-lab coliform prices
12 states print a standalone price for a coliform bacteria test at a state, public or university lab in the pages we read. These are prices as printed, not part of the score:
| State | Coliform price as printed |
|---|---|
| Wisconsin | $35 |
| Michigan | $23 |
| Florida | $40 |
| Idaho | $21 |
| Missouri (printed as a handling fee) | $10 |
| Oklahoma | $33 |
| South Carolina | $20 |
| Louisiana (online orders add a service fee) | $40 |
| Maine | $27 |
| Vermont (kit price) | $14 |
| South Dakota (total coliform only) | $20 |
| Georgia (university lab, not a state health lab) | $40 |
Prices change: check before you order. For the test itself, see coliform bacteria in well water.
Limits
This study shows where the official lists put certified labs and what the official pages say about programs and laws. It cannot show how long a real test takes to arrange, what a private lab charges, or how many owners test.
- Flagged lists. Several lists are ranked with a caveat. Pennsylvania's, Georgia's, Puerto Rico's and Nebraska's lists are stale: the newest official versions we could get are more than a year old, or (Pennsylvania) come from reports printed in June 2024. Parts of Michigan's and Alabama's lists are more than a year old, while their other lists are current. Massachusetts, Wyoming, Mississippi and Georgia are partial: Massachusetts' list is MassDEP's list for private well owners and residential customers, Wyoming's lists only labs EPA Region 8 certifies itself, Mississippi's lists only in-state labs, and Georgia's microbiology list covers commercial labs only. The "clean" figures leave all of these out (Clean = ranked lists with no stale/partial flag; excludes Wyoming, Michigan, Massachusetts, Puerto Rico, Pennsylvania, Alabama, Nebraska, Mississippi, Georgia). Our by-state table records the detail per state.
- Hawaii and Puerto Rico coverage. Most of Hawaii's in-state labs and several of Puerto Rico's have no address on the list, so they cannot be placed in a county. Coverage is scored only where at least 80% of a state's in-state labs could be placed, so it is left out of both scores. Their well users in counties with no placed lab still count as "not covered" in the national total above. Puerto Rico's 4,708 well users also make its lab density of 14.87 per 10,000 meaningless as a comparison.
- Homeowner marks are not comparable across states. Five states mark commercial, public or outside samples, and Vermont marks by highlighting. In California, Louisiana and Vermont some labs on the list carry no mark, and in the states where a separate page names a few labs, the share is a floor. This is why the component is used only for the 7 states whose list marks every lab.
- Lists differ in scope. Some lists cover only certain tests. Wisconsin's list on this site is its coliform-bacteria labs, for example, so its lab count is a count of bacteria labs.
- The well population is from 2015. USGS's county estimates of people on self-supplied domestic water are 11 years old, and some of its Virginia independent-city figures look unreliable. We use the state totals as published.
- "None found" means none in the pages we read. For free programs, home-sale laws and state-lab prices, "none" means we found nothing in the official pages already in our fact-checked state guidance. It does not mean none exists. Local and county programs are not counted.
- A county line is a rough measure of distance. A lab just across the line may be closer than one in the same county, and an out-of-state lab may accept mailed samples.
What to do if your state scores low
- Open your state page for every lab on your state's list, including out-of-state labs, and any program we verified. The lab finder filters by contaminant and homeowner marks; for bacteria, start with bacteria-certified labs.
- Call the lab before you collect: does it take household samples, on which days, how long can the sample travel, and does it ship a kit? Then see our guides on how to test well water and how to collect a sample.
Getting the data
Everything behind this page is in one by-state table: one row per state list, with every component and component score, the index, the rank, list versions, official source URLs for free programs and home-sale laws, and caveats (counts only, no lab contact details). We do not publish it as a download. Journalists and researchers can request the data here: say who you are, where the work will appear and which data you need, and we will reply.
Questions people ask
What is the Well Owner Access Index?
Which states score highest and lowest?
How many well users live in a county without a certified lab?
Which states offer free well water testing statewide?
Does any other state require a well test when a home is sold?
Can I use this data?
- U.S. EPA, Private Drinking Water Wells (last updated November 2, 2026) (accessed 2026-11-04)
- USGS, Estimated use of water in the United States, county-level data for 2015 (Dieter and others, ver. 2.0, 2018) (accessed 2026-11-01)
- U.S. Census Bureau, 2020 ZCTA to county relationship file (accessed 2026-11-01)
- Official state drinking-water laboratory certification lists (45 lists; versions and URLs per state on each state page) (accessed 2026-11-03)
- Iowa DNR, Private Well Program: Well Testing (accessed 2026-11-04)
- Iowa DNR / Iowa HHS, Private Well Grants Program: Guidance on Qualifying Expenses (updated Jul 8, 2026) (accessed 2026-11-02)
- Idaho Department of Health and Welfare, Drinking Water and Private Wells (page last updated 11-2-2026) (accessed 2026-11-03)
- Wisconsin DNR, Wisconsin PFAS Private Well Testing Program (accessed 2026-11-01)
- Colorado Department of Public Health and Environment, PFAS Testing and Assistance Program (PFAS TAP) (accessed 2026-11-02)
- New Mexico Environment Department, news release: NMED offers free well water testing statewide (August 13, 2026) (accessed 2026-11-03)
- New Mexico Environment Department, Free Well Water Testing (no date printed) (accessed 2026-11-03)
- South Carolina Department of Environmental Services, Well Water Quality Testing Services (no date printed) (accessed 2026-11-03)
- Oregon Health Authority, Lower Umatilla Basin Groundwater Management Area: Make sure your well water is safe (accessed 2026-11-02)
- California State Water Resources Control Board, private domestic well testing page and Well Testing Program Directory (June 2026) (accessed 2026-11-02)
- Washington State Department of Health, Testing your water (accessed 2026-11-01)
- New York State Department of Health, Private Well PFAS Testing and Mitigation Rebate Pilot (accessed 2026-11-01)
- Oregon Health Authority, Domestic Well Safety Program: Domestic Well Testing Act and Real Estate Transaction form (ORS 448.271) (accessed 2026-11-02)
- Oregon Health Authority, Oregon Administrative Rules 333-061-0305 to 333-061-0335, Domestic Wells (effective Jan 1 and Feb 1, 2026) (accessed 2026-11-02)
- Rhode Island Department of Health, Testing Your Well Water (last updated October 22, 2026) (accessed 2026-11-03)
- Rhode Island Department of Health, 216-RICR-50-05-2 Private Drinking Water Systems, section 2.12 (accessed 2026-11-03)
- Maryland Code, Real Property § 10-713, added by 2023 Laws of Maryland Chapter 587 (HB 11, Private Well Safety Act of 2023), effective October 1, 2024 (read from the Internet Archive capture of October 17, 2026 of the official enrolled chapter) (accessed 2026-11-10)
- Connecticut General Statutes § 19a-37 (current, chapter 368a) (accessed 2026-11-01)
- New Jersey DEP, Summary of Amendments to Safe Drinking Water Act Rules (N.J.A.C. 7:10) and Private Well Testing Act Rules (N.J.A.C. 7:9E) (rules effective June 1, 2020) (accessed 2026-11-04)