The State Flagged Llano County's Water. Your Private Well Isn't Covered.

Llano County sits on an official state list of Texas counties where groundwater must be tested for radioactivity before a public water system can use it. The county shares that designation with Hill Country neighbors like Gillespie, Kerr, Mason, San Saba, Burnet, and Travis, all pulled into the same regulatory net because of the same underlying rock. What the designation does not do is test the well that will actually supply the house, barn, or guest cabin on the acreage you're evaluating. That gap between what the state flags and what the state checks is the thing worth understanding before you write an offer on land in Llano County.

Why the county made the list

The geology here is unusual even by Hill Country standards. Llano sits at the center of the Llano Uplift, a dome of Precambrian granite that pushed to the surface long before most of the rock in the rest of Texas had formed. The Texas Water Development Board's own description of the Hickory Aquifer, the water-bearing formation that runs beneath much of this uplift, notes that groundwater there is mostly fresh, generally under 1,000 milligrams per liter of total dissolved solids, but that naturally occurring radioactivity may exceed the state's primary drinking water standards, with radionuclides derived directly from the Precambrian granite rocks of the Llano Uplift. The upper part of the aquifer also tends to carry excess iron, another naturally occurring issue that can affect taste and occasionally exceed drinking water standards on its own.

The Texas Commission on Environmental Quality confirms this pattern on its statewide drinking water page, stating plainly that radionuclides in Texas drinking water most often come from naturally occurring radioactive material, typically in groundwater from the Hickory Aquifer in Central Texas. That's the regulatory basis for Llano County's spot on TCEQ's Table 1, the formal list of counties where any newly constructed public water supply well must be tested for gross alpha particles and combined radium-226 and radium-228 before it can be approved for use.

The rule only reaches one kind of well

Here's where the gap opens. TCEQ's radionuclide testing requirement is written for community water systems, non-transient non-community systems, and transient public water systems, the kind that serve subdivisions, businesses, or public facilities with multiple connections. A single-family domestic well drilled to serve one house on one tract of acreage falls outside that framework entirely. Nobody at the state level is ordering a radionuclide panel on it, and nobody is required to.

That distinction matters because most rural acreage in Llano County depends on the second row of that table, not the first. The state's own well-completion checklist reinforces the point in its own language, warning that the analysis for radionuclides takes longer to complete than other constituents and telling public system operators to plan accordingly. A private buyer closing on a thirty-day option period doesn't get that same built-in runway unless they ask for it themselves.

What the Tow example actually shows

This isn't a theoretical risk confined to a state database. A short distance from Llano, in the unincorporated Lake Buchanan community of Tow, the Lower Colorado River Authority has operated a dedicated radium-removal treatment system for the Tow Village Water System. Reporting tied to a separate water-quality dispute over a proposed rock-crushing operation near Burnet cites LCRA's own documentation that raw Hickory Aquifer water feeding that system tested at roughly eight times the federal combined radium limit, with gross alpha readings near 140 picocuries per liter, well above the 15 pCi/L threshold that triggers TCEQ action for public systems.

Someone had to build actual infrastructure to bring that water down to a safe standard. That's the clearest evidence available that the county's spot on TCEQ's list reflects a real, measurable condition in specific parts of the aquifer rather than a bureaucratic formality. It also means the range of outcomes across the county is wide. A well two miles away could test clean. The only way to know which well you're getting is to test that specific well.

The new form that doesn't close the gap

Texas just changed what sellers have to say about water, and the timing lands right in the middle of this issue. The Texas Real Estate Commission adopted a new standalone disclosure, the Water Notice about Groundwater and Surface Water Rights, on May 4, 2026. An updated general Seller's Disclosure Notice took effect May 28, 2026, and the new Water Notice itself took effect July 1, 2026. For the first time, sellers of most residential and rural property are required to answer specific questions about wells, groundwater rights, surface water rights, and whether the tract sits inside a groundwater conservation district.

The exemption from that Water Notice is narrow. A seller only qualifies if there's no well on the property, no pond or lake or water tank, no surface water permit, no severed or sold groundwater rights, and the property receives water solely from a city, municipal utility district, water supply corporation, or private water company. Almost no ranch or acreage listing in Llano County meets all five conditions at once, which means the new form will apply to the overwhelming majority of rural transactions here going forward.

What the form does not do is require anyone to test anything. TREC's own published FAQ on the disclosure states that the notice is a disclosure of the seller's knowledge as of the date they sign it, not a warranty, and not a substitute for the buyer's own inspections. A seller who has lived on the property for years and never had the well tested can honestly check the box that says they don't know the water quality and move on without violating any rule. The paperwork changed. The underlying obligation to actually test the water, for the buyer's own protection, did not shift to anyone new.

What this means before you write an offer

For a buyer evaluating acreage in Llano County, the practical takeaway is straightforward. Treat the county's presence on TCEQ's radionuclide list as a reason to test, not as evidence that testing already happened.

A useful panel for a private well here typically includes:

• Gross alpha particle activity, compared against the federal maximum contaminant level of 15 pCi/L
• Combined radium-226 and radium-228, compared against the federal maximum contaminant level of 5 pCi/L
• Iron, given the Hickory Aquifer's documented tendency toward elevated levels in its upper zones

Because radionuclide analysis takes longer than a standard bacteria or nitrate panel, the sample needs to go out early in the option period rather than in its final days. If a result comes back elevated, TCEQ's own guidance on treatment for public systems lists the same tools available to a private homeowner: reverse osmosis, ion exchange or greensand filtration for radium and uranium, or blending with a cleaner water source. None of those options are exotic or unaffordable, but all of them are easier to negotiate into a contract before closing than to discover after.

A few direct questions

Does an elevated radium or gross alpha reading always mean the well is unusable? No. It means the water exceeds the federal standard designed for lifetime exposure through a public system, not that the water is unsafe for any use. Treatment options exist and are used successfully across the Hickory Aquifer region, including at the Tow system itself.

If the seller checks "unknown" on the new Water Notice, is that a problem? Not under current rules. The disclosure is based on the seller's actual knowledge. If they genuinely never tested the well, marking it unknown is compliant. That's exactly why the buyer's own test during the option period matters more than the form itself.

Does any of this apply if I'm planning to drill a new well rather than use an existing one? TCEQ's mandatory testing trigger is written for public water systems, so a new private domestic well still falls outside that specific requirement. The aquifer chemistry underneath the property doesn't care whether the well is old or new, which is why testing your own water, regardless of the well's age, remains the only way to know what you're getting.

Water quality on a piece of Hill Country land is never something a listing photo or a county-level flag can settle for you. If you're evaluating acreage in Llano County and want a straight answer on what a specific well needs before you write an offer, TXR Texas Real Estate can walk you through the testing, the timeline, and what the new disclosure form does and doesn't guarantee.