tsbinia
it may have been the resistance on the hub of the couplings (a lot of drag). next time try using the pvc with the factory belled ends and make sure the female end of the pipe is in the back and the male is attached to your machine. I wouldn't worry about pvc valve manifolds.

Two thoughts:

#1 "needed to be pounded" doesn't sound right. I've never had to pound PVC (though my experience is limited to 1/2", 3/4", and 1" pipe).

#2 I'm not sure PVC pipe connected with standard fittings is rated for pipe pulling.

I've noticed the pipe that devinglanz is talking about in 20' lengths. In addition to the female end being bell shaped (reduces drag from sharp corners), the female end provides something like 6" to 8" of pipe length to make the glue joint. A standard fitting has less than 1" of pipe length for gluing. You also double your joints with standard fittings (i.e. each pipe is glued to the fitting separately). But with the pipes devinglanz is talking about, the fitting is a molded part of the pipe, so you only have one HUGE glue joint where the pipes meet.