I can get very close, but I've never been able to find it. I suspect because it is long gone.
Opa discovered a natural mineral water spring on the farm sometime after the war. He decided to start bottling and selling it, which he did rather successfully through the 1970's. Then, unfortunately, through a good deal of political shenanigans, strong-arming, and outright thievery, he lost his "rights" to that water. It was declared some kind of a public resource or something which, apparently, just because it bubbled up on his land, didn't necessarily give him the "rights" to it. It was one hell of a sordid tale, one that broke his heart. He died a very wealth man, but was unable to pass the business down to any of his sons.
On a kind of a side note, he managed to live long enough to where I brought my wife to meet him when she was pregnant with our first child, and his only great-grandchild. She doesn't speak German and he never spoke English, but he had no trouble communicating to her his profound joy. He passed about a week after we got home. 97 years old, WWI vet - a bicycle messenger in the trenches, and then later a mule packer in the Balkans.
Anyway, the business survives today. Funny, it never went "public", and some big German conglomerate took it over. So I can find that, it was on one corner of the farm. I just can't remember where the farm house was from there, which direction and how far. I just remember it seemed a huge farm to a kid.
Here is the bottling business, Volkmarser Mineralbrunnen' website:
Volkmarser - Waldecker
Here it is on Google Maps:
https://www.google.com/maps/place/Volkmarser+Mineralbrunnen+Waldhoff+GmbH+%26+Co.+KG/@51.4066523,9.1338052,3725m/data=!3m1!1e3!4m5!3m4!1s0x47bb0dd366010d27:0x86d04 916effeb892!8m2!3d51.4066823!4d9.137461
So, yeah, I can get close, but just can't nail it down.