Thanks
@GBBUDD and everybody else inputs........... They don't want a external pump. It would ruin the ambiance. The place has formal gardens with beautiful flowers.
You can see the skimmer box / pump box lower corner of the picture.
They are concerned about power use and monthly cost. Both work 1/2 of the year in Egypt on the pyramids, very educated, fly around when back here giving talks about the work over there.
A sister lives at the house all year, to remove a external pump would be more of a burden on her. A really neat old stone house.
I only use externals except for the hot tub pond, and that is a tiny Laguna. I have always liked externals,
I found a off brand, home depot, that says it is 6000 gph, if their head pressure is 10 feet, I think it is lower, the gph should be around 3000. The water fall is around 5 feet, add some line and connections head pressure might be 10ish feet. The picture above you can see the top of the water fall the filter box is up there, the pump input is around 2.5 feet lower. So the line is around 2.5- 3 feet above the output of the pump.
And if it does not work we can take it right back to HD. pg 6600
https://www.homedepot.com/p/Lifegard-Aquatics-6600-GPH-Pond-Pump-R800004/204855646