The following stopped progress for a day and a half:
If you look directly below the valve, you will see the culprit. Plumbing is a bitch.
We originally had a leak at the connection to the sink. It was a flexible plastic pipe with the nut permanently attached. My friend cut the original pipe, added a different type pipe, a shut off valve (this is not necessary and was sold to him when I was on the other side of the store. He did not know that if the pump is off, the water is off) and a compression connector to piece it all together. The original leak is gone. The compression connector does not leak. The unnecessary valve leaks. We tried thread tape and tape on the outside. Still leaking.
Finally, I had enough and decided to push on with the rest of the bathroom. We can fix this after more research, I’m didn’t want to waste more time. We will probably remove the valve and figure out a way to connect everything with something else.
The only reason we didn’t already do that was because we had already been to the store 4 times that day alone.
I had never seen my friend remotely angry before. He is a really even kind of guy. Eyeglasses may have been thrown.
We laughed, we (I) cried, we carried on.