Wow, what a difference the water heater rescue kit makes! Over the weekend I installed the curved dip tube, made some heat traps out of leftover copper tubing, and flushed out the system. The water was roaring out of the hose into the sump.
Now the only problem is my sump pump does not seem to appreciate the soaking, and is refusing to turn on when the float rises. I’ve never worked on a sump pump, but it looks like I’ll have to start. Fortunately, I have a water-powered backup pump that can take over until I figure out what I did to the electric pump.