Position of the water pipe unknown

No one has ever lived on our building plot, i.e. existing pipes are basically "unused". As long as there is no steel pipe, according to the employee they can be used without any problems. As I said, the basic issue was the request for a pipe map, which revealed that the water association does not know exactly where and how it lies.

However, since a valve is installed on the main water line and a blue water sign with the corresponding distance data for the valve is located directly on our property, logically there should be an (empty) water pipe there.

[*]Our plot is a building gap, i.e. the plots to the left and right of us are developed.
[*]The street was redone a few decades ago and all imaginable utilities (water, sewage, electricity, gas, fiber optic, ...) are connected to all plots.
[*]In front of our plot there is a blue water sign (like at all the others as well) with position data for the valve.
[*]The sewage pipe (branching from the main sewage line via valve) lies about 80-100 cm on the property (found by exploratory excavation).