Have you ever dealt with a dirty water pump that just wouldn't
drain the last few inches? Is there a simple solution?

I bought a 1 HP Harbor Freight 69300 dirty water pump to drain
a green pool but it won't turn on at low water levels:
https://c2.staticflickr.com/6/5458/1...ee73cc98_c.jpg

Even with the obnoxious float switch manually set to permanent on,
the pump stops pumping with plenty of dirty water left to pump out:
https://c4.staticflickr.com/8/7699/1...45741c9b_c.jpg

I'm currently shoveling the water into a garbage can and then
pumping it out from the garbage can:
https://c1.staticflickr.com/9/8811/1...f798a613_c.jpg

But, pumping at 50 gallons per minute, I have to constantly run
to the GCFI and pull the plug to shut it off before the garbage
can runs dry:
https://c4.staticflickr.com/8/7642/1...c37715ab_c.jpg

Currently I have a 2-inch pool vacuum hose connected to the
1.5-inch outlet (female NPT thread) in the steel body of the pump:
https://c1.staticflickr.com/9/8805/1...d602a39d_z.jpg

But, I'd like to see if I can jury rig *something* (a rubber hose
perhaps?) to go on the *underside* unthreaded inlet of the pump:
https://c2.staticflickr.com/6/5443/1...ed88636b_z.jpg

What could I shove into that inlet which will allow the pump to
go shallower than the three or four or even five inches it seems
to currently stop at?

I have a few 1.5-inch NPT fittings which go on the *outlet* of
the stainless steel body:
https://c4.staticflickr.com/8/7644/1...bc0500f9_z.jpg

The specs for the pump "say" it drains down to 1-3/8 inches:
http://www.harborfreight.com/1-hp-st...gph-69300.html

But, the owners manual says it stops at 3 inches (which it seems to do):
http://manuals.harborfreight.com/man...9999/69300.pdf

Have you ever dealt with a dirty water pump that just wouldn't
drain the last few inches? Is there a simple solution?