ARRRRGH.
Rule number one -- no, rule number zero, when buying stuff from Home Depot -- is to always check that what you grabbed from bin X is, in fact, what should've been in bin X. Like the other day when I grabbed a ballvalve from the 1" OD box, and got home, and it turns out it was a 3/4" ballvalve, so: entirely useless. Likewise, at the same time I grabbed a replacement sprinkler head from the 90 degree box, and it was a 180 degree sprinkler head.
NEVER TRUST ANYTHING.
Sigh.

With that said, I got the sprinkler system waterbreak taken apart and the trashed valve replaced, plus most of the other pieces I had to remove put back together save for a 20 cm length of PVC tubing that refused to come loose from the barbed plumbing fittings. Sooo I went to HD and bought some new tubing and will cut the old tubing off the existing fittings with a box knife, I guess.

I stapled up the 6 mil sheeting along the west wall of the bathroom, ready for cementboard. The east wall is waiting for the replacement shower mixer/valve.

Right now I am obsessed by pulsejets and H2O2 rockets, and the thought of building my own.