Finding pin holes in a closed loop system

[sphelps]

Your pipe size is too small for what you're doing, by my rough calculations you've got over 6 feet of head pressure being created in that intake plumbing. If you jump up to 1.5" you're only adding about 1 foot, 2" you adding less than 1/2 a foot.

That's assuming your pump is wide open on the other end with of course it is not but to me the obvious solution is to swap out the plumbing for at least 1.5" or even 2". This will mean you'll have to re-drill that sump hole.