Wood – What are the black spots on the basement ceiling

DriCore is a subflooring that is specifically designed for light or occasional moisture. The portion of the product that touches the floor is all plastic and it lifts the upper portion more than 1/2 inch away from the concrete floor. The joints are fairly tight (although not actually sealed). It is intended to allow water to accumulate in the open spaces under the plastic waffling and drain or seep away without reaching the upper layer.

The particle board that makes up the surface is impregnated with resin and is meant to be fairly impervious to moisture. If you have an actual flood that occurs which is high enough to reach and damage the surface, you have much bigger problems.

An assortment of thoughts which may or may not be applicable to your situation:

In general, larger capacity units are more efficient than smaller capacity units, according to Consumer Reports. They suggest buying a 70 even you don't think you need it.

If you're using the built-in bucket, the dehumidifier stops whenever that becomes full. You have to empty it as frequently as necessary... or set up the unit to drain into a sink or otherwise move the water out of your house automatically. (Mine has been draining into a pump which in turn empties into the washing-machine drain.)

If you have water coming in as fast as the dehumidifier can pull it out, you won't make progress. How well sealed is that basement?

Make sure you have allowed enough air circulation around the dehumidifier and into the rest of the basement.

Dehumidifiers are somewhat notorious for recalls. If you really think yours isn't working properly, you might want to check with the manufacturer to see if there's a recall that hasn't been announced yet.. (The last two I've owned were both recalled; the first seemed to be working OK for me, the second was clearly bad from the moment I turned it on).

Good luck.