Oops!

Did I say it was obvious where the leak was?  Well, this pipe had actually split all the way down to the cutoff valve.  Ah well.  So it was back to the old drawing board.  After another half hour's work replacing that valve and the tee:

Voilà!  This is plumbing already under pressure -- I have a working toilet (now much cleaner) and a working hose tap for my bucket.  I have returned to a good deal of civilization.

Next plumbing target: the carriage house.  The water enters the house on the east side, and the supply line runs down the entire middle of the basement, to exit at the west side, bound for the carriage house.  If I'm really, really lucky, the buried pipe between the main house and carriage house didn't burst.

Anyway, this plumbing, and cleaning the first toilet, was all I got done today, house-wise.