Right of way - Old drainage of unknown origin

That's how it is, why should you, who has absolutely nothing to do with it, have anything placed on the property?

If there's nothing in the land register, they can all go to hell..

And if they want something, I would have it gilded, every time they want to go into my garden.

The neighbor, from whose property the drainage leads into the new development area, claims to have no idea where the drainage comes from and does not want to contribute to finding a solution.

Well, then the solution is obvious ...

We have now been told that the pipe is probably so old that if it gets blocked somewhere, it would burst elsewhere.

... because that’s exactly how it is. So: the neighbors you feel sorry for only need to block the drainage right at the border between their property and the property of the neighbor Jucktmichnicht. Then it will burst at his place, and suddenly his interest in finding out who caused the damage will awaken. However, the neighbors next to you / "below" him should be warned ;-)

Thank you again for your help! Legally speaking, would this neighbor who does not want to be involved be obligated to take care of the issue? The drainage does come from his property, but according to his own statements, he was not aware of it, and possibly the origin is elsewhere (by the way, this neighbor's property is huge and consists mainly of meadow).

the plot of land of this neighbor is by the way huge and mainly consists of meadow).

Meadows with drainage are also being drained, that can have been like that for a very long time

Would this neighbor, who does not want to be involved, be legally obliged to deal with the issue? The drainage does come from his property, but according to his own statements he knew nothing about it and possibly the origin is elsewhere

If you do not take action to return the ball towards the source, then I see a danger: that the municipality will see urgent need for action, have you condemned to tolerate a measure, and Mr. Neighbor GoAwayCan’tTouchMe can continue to shirk responsibility, even though ...

(this neighbor’s property is by the way huge and consists mainly of meadow).

... this points out that he is not insignificantly involved in the entry of the problematic water. Whether his great-grandfather told him about the pipe does not matter to the water. It becomes a problem for the neighbor, and it threatens you with the compulsion to bear the burden of a remedial action. Defend yourselves, otherwise the wheels of administration will work against you!