Have 60A 220V circuit, want to use one 110V leg of it. Can i?
Since I'm loosing confidence in the idea of using the single relay to control both circuits, I now think the right answer is to simply buy ANOTHER RELAY. I can get a less expensive 110v capable relay for the drain-valve circuit and wire them both to the same 24V signal from my digital IO controller.

This keeps all of the line voltage stuff "clean" and normal. 

I'm not sure why I didn't think of this before.

[EDIT: 12pm 3/27] I'm 90% finished with constructing this thing. One more trip to the hardware store and the use of a my toner to find the 24v wire in the attic and it should be up and running. Here's a pic of the two pump-start relays mounted and mostly wired:


[EDIT: 7pm 3/27] Done! Works like a champ. Here are some pictures of the final result: