OK, let's try to be scientific here, since we're talking about a bunch
of money. If my pump specs recommend 1.25" diameter tubing for the
distance I'm pumping, won't the friction on the tubing ID be great, if
it's got the spiral texture? So, to my mind, smooth tubing would be
much better, assuming I won't need to take any tight bends, so no
kinking.

With smooth tubing, clear PVC from Home Despot at 1.25" is expensive!
I don't need vac tubing at all. I could hard pipe with rigid PVC but
soft would be easier. Has anyone used the black tubing used for drip
irrigation? Seems that should hold the pressure. Maybe I should just
call my pump company hotline (Oase). What does pool tubing go for?

Thanks again. There's a big hole in my ground yawning to be filled
with water!

--Rob