Observation: There seems to be a bit of a leak in the downstairs bathroom sink. Turning off the shutoff valves to it stops the leak.
Solution: After experimenting some, determine that the faucet itself has a leak. Remove faucet, replace with standard issue faucet. Faucet no longer leaks.
Observation: The cold water shutoff valve now drips. (I suspect roomie over-opened it, and it was ~30 years old, so it was already on the verge of failure.)
Solution: Obtain replacement shutoff valve. Turn off water main, replace shutoff valve.
Difficulty: The compression rings were pretty much stuck on the tubes. The one on the larger tube came off easily, the other one took a bit of doing.
Observation: The smaller tube side of the shutoff valve now drips.
Solution: Obtain pipe cutter and replacement compression ring, etc., shorten pipe past the area which was noticably scratched and dented.
Problem: The pipe no longer reaches to the shutoff valve.
Solution: Go buy five feet of flexible copper pipe and a replacement for the valve at the OTHER end (the one connected to the sink.)
… So, okay, put the valve on the pipe, run it through the floor, connect everything up.
Observation: Very slight drip on that side of the shutoff valve.
Solution: Another quarter turn.
Total cost: About \$80-90 in materials plus about two hours’ time. (I’m not even including the saga of the silicone caulk, the search for a reamer, or some of the other side quests.)
… But at least I didn’t have to call a plumber, right?