Pszemol wrote:
Have you used thin-walled PVC or regular SCH40?
SCH40 1" pipe has very thick wall - its internal diameter,
where water flows, is similar to thin-walled 3/4 pipe.
Replacing regular schedule 40 pipe with thin-walled
one and THE SAME OUTSIDE diameter will make a big
difference in the amount of water the pipe can handle.

The pipe is 1.5" connected to the 1" bulkhead with a reducer bushing.