Basically, I was super tired getting home from an event last night and didn't even notice the water hadn't stopped flowing normally. It's quiet so I don't normally hear it.
Apparently at some point a couple hours in a fitting in my drip setup blew, flooding my peppers planter entirely and in the process burning through nearly 4000 liters of water before I caught it on my way out the door to work this morning.
I've since learned there's a Z2M command to start watering on a timer, but I didn't know that before and trusted Whisper to not fuck this up. My fault.
Don't think my water bill company will be amenable to it. I'll call and ask but, fuck.