A drilled well that reaches a confined or deeper unconfined aquifer, typically more than 100 feet deep.
A deep well taps a more protected, more reliable aquifer. In Utah, residential deep wells commonly run 200 to 600 feet; agricultural wells often exceed 800 feet; municipal wells can pass 1,000 feet. Deep wells cost more upfront but generally deliver better water quality, more stable yield through drought, and longer service life than shallow wells.