Shallow well or deep well: the decision is about what the water is for

What each one actually is

A shallow well draws from the sand above the clay confining layer. It may be a driven sand point, a two-inch well with a jet pump at the surface, or a larger bore that simply stops above the clay. A deep well is cased and grouted through the clay into the Floridan limestone and carries a submersible pump on a drop pipe near the bottom.

The 25-foot problem

A jet pump lifts water by suction, and at sea level suction gives out at roughly 25 feet. A shallow well whose level drops below that in a dry spring loses prime, and the household hears the pump humming with nothing at the taps. A submersible pushes from below and has no such ceiling, which is why every well of real depth around Jacksonville runs on one.

Exposure and chemistry

The shallow zone is open to whatever happens at the surface: drought, runoff, the neighbour's fertiliser, and on a lot with a septic system the drain field's effluent. It also tends to carry iron and tannins, which stain. Floridan water is buffered from all of that by the clay, and its own complaints, hardness and sulfur, are predictable and treatable.

Where the line falls

Irrigation on a utility-water lot: shallow, usually, with an iron check first. Drinking water on a lot with a septic tank: deep, almost always, because the setback and the exposure both argue for it. Livestock, wash-down and outbuildings: shallow where the table is steady. A house that irrigates hard through spring: deep, or the lawn and the shower compete.