You're probably looking at an in-floor connection to the local
water-table, rather than what you seem to perceive as a piped drain.
Often it's just tile pipe to nowhere.

I've seen strange things happen with water level in such
"hole-in-the-floor." Like, after decades of a dry-hole, suddenly water
poured forth. Seems something changed subsurface water situation in the
area of the house. Then it flooded another half-dozen times.

Simplest solution: float-valved sump-pump.
Severe case: work on drainage around house perimeter.

J