Exempt Well

Arizona sorts wells by pump size. A.R.S. 45-402 defines an exempt well as one whose pump has a maximum capacity of not more than thirty-five gallons per minute, used under A.R.S. 45-454, the section on small non-irrigation wells. Fit a bigger pump and it becomes a non-exempt well.

What the exemption is worth depends on where the lot sits. Inside an Active Management Area (AMA), a basin the state manages tightly, pumping from a non-exempt well takes a grandfathered right, a service area right, or a withdrawal permit. An exempt well needs none of them. Outside an AMA, the Arizona Department of Water Resources (ADWR) says wells face fewer requirements to begin with, so the exemption buys less.

Exempt does not mean unregistered. You file Form 55-40, a Notice of Intent to Drill, before any well is drilled, deepened, or modified, and a licensed well-drilling contractor has to do the work. ADWR has 15 days to process the notice under A.R.S. 45-596(D). If the water will serve a home on five acres or fewer, your county health authority reviews the application first.

For example, a buyer on a five-acre Rio Verde Foothills lot files the 55-40 and gets a registered exempt well. None of that guarantees water. ADWR's approval does not override a local ordinance restricting wells, and its well-spacing rules, written to limit drawdown at neighboring wells, skip exempt wells inside an AMA and every well outside one. A legal well can still go dry as the neighbors pump.

That risk is why owners on unincorporated land keep a fallback, usually hauled water into a cistern. An exempt well is a legal status, not a type of hardware. The hole, casing, pump, and tank match any private well. Two identical wells next door can differ only in the pump, and only one is exempt.