Is a dehumidifier a clue that a basement is sometimes wet?

Well, wet no. Humid, yes. There is a difference and I explain.

Basically all below grade structures are prone to moisture. They are boxes of concrete or stone, buried in moist, lose soil.

When it rains or snows heavily, the hydrostatic pressure generated by and over saturated soil around the foundation walls, causes the water to seep in through the porous concrete, or cracks on the wall.

Clogged gutters, downspouts discharging too close to the walls, improper grading and plants that need constant watering close to the house make matters even worse.

If the foundation has good drainage system in place, usually indicated by the presence of a sump pump or some other clear sign that any water pouring around the foundation is being collected and properly diverted away from it, your basement might be a bit damp but not exactly wet. That means no serious leaks or heavy seepage. Only a bit of moisture coming in due to capillary action and maybe some humidity from the air.

This is the kind of moisture the dehumidifier is probably addressing and it is a great addition to a home, because it protects the home from mold and dust mites (those organisms need high humidity levels to thrive).

However, the presence of a dehumidifier alone is in no way a sign that the basement is either dry or wet.

To make sure, you need to check the drainage system, where and how it discharges, as well as gutters, downspouts and the grading, which should slope away from the foundation wall.