How low should I drill holes in my sump pump basin? Should I drill them at the bottom?
Generally you want the holes at the bottom.  This allows you to remove the maximum amount of water from under your slab or foundation.  You will not pump out the entire ground water supply as it takes a finite amount of time for ground water to move toward a low-pressure area.
So your sump pump will create a &quot;dip&quot; in the ground water level around the sump but that's what you want to happen.