I purchased a home last fall just to discover, come spring, that it was on a natural spring.
It turned out that the spring is water table dependent and as such was not present during the time of the home inspection as water levels were lower. Upon tearing up the carpet I had discovered cracks in the floor that were patched over and that the water was taking said path and, when breaking open that path, the contractors had discovered that the area around the path was hollowed out by the water.
The only thing indicated on the sellers disclosure was that they had sump pumps that ran no structural or foundation issues were indicated, however I am unsure if a spring is required to be disclosed in PA
Note: When I say there is a natural spring I mean 4000+ gallons an hour from 1 of the pumps alone. And city has tested the water disowning it as definitely ground water