The Plumbing Is Completely Broken.
The plumbing was a mix of original cast iron and old copper (which crumpled in our hands as we removed it). It was clear that the plumbing in place, in the bathroom, once resided somewhere else. From the look of it, the major plumbing had been moved sometime previous. It was cut up. Twisted about. Poorly overlaid. And reconnected using unions which had grossly deteriorated over time. On top of that the drains were rotted and every valve leaked.
Note: The drains are rotted because there was constant water running. There was constant water running because every valve was worn out. The constant water both inside and outside the drains caused major rot. It would have cost pennies to replace the warn valve parts but instead the problems were ignored.
Lesson: Home owners take care of your investments. Simple maintenance over time saves tens-of-thousands in repair at time of sale.
Actually: If the previous owners of this property had followed this simple rule then they could have sold it instead of forfeiting it to the mortgage insurance company.
So... We decided to replace the plumbing. Completely. We cut off the drain at a convenient reattachment point and stripped the house of all it's plumbing.
And... Since we had the bathroom floor open up. We had great access to the service-main and the majority of the difficult work (poor access) was now very easy with open access to the crawl space. We decided to run a shut-off up through the sub-floor so we had control of the water without having to crawl to the waters entry point under the house. Unfortunately the cities main valve leaked. If you look closely here you will see an additional gate valve at the city main as wall as our above floor shut-off. We needed to do this because the leaky city valve prevented us from soldering the copper we were attaching to it.