Boulder County puts private well quality squarely on the owner: 'As a well owner, it is your responsibility to make sure your private well water is safe.' There's no county testing mandate tied to selling. The state recommends annual coliform/nitrate testing and a fuller baseline panel for never-tested wells — and lenders often require exactly that evidence at sale.

County requirement	None at sale on the county's private-well page — testing is the owner's responsibility.
Recommended baseline	For wells with no testing history, CDPHE's recommended baseline covers arsenic, hardness, coliform bacteria, copper, fluoride, iron, lead, nitrate, nitrite, and uranium; annual testing at minimum for coliform, nitrates, and nitrites.
Statewide filing	Every Colorado well sale needs the free DWR change-of-owner filing so the well permit follows the property. source ↗
County contact	Boulder County Water Quality Program, 303-441-1564.

Details to confirm with the county

We couldn't confirm the following from Boulder County's official pages. Check these with the county before you rely on them:

• Whether Boulder's septic Property Transfer Certificate packet ever asks for a water sample — the county's well page doesn't, and we haven't yet confirmed the packet page by page.

Verified July 2026 · Source: Boulder County — Private Wells and Water Quality