Dave to give you an idea of the amount of water here is a pic of our waterfall. It uses a 1 1/2 hp 3000 gph sprinkler pump. The head is about 6 or greater when the pond is down. It fills a stream that is about 2 ft wide and 8 feet long before it drops over the edge. I'm using 1 1/2 polly pipe the size that the pump inlet and outlet is designed for and have it plumbed to a 1 inch manifold made from pvc that spreads the water out at the outlet of the falls. I think with the pump you are using assuming it is not to far from the pond or water fall should do a great job with what you are trying to do. That is unless you want a very massive amount of water. As pointed out above the most important thing in water fall design is to get the rocks set level so the water will spread and cover the entire ledge as it drops to the next.
You can see a short clip of it in the second video in this thread and hear the sound of it.
http://www.pondboss.com/forums/ubbthreads.php?ubb=showflat&Main=13785&Number=168922#Post168922Good luck and please post pic's when you are done. I love building water falls I have dreams of building more in the future but to many irons in the fire for now.
