Huskerduck- what you have all said makes sense to me. I never had considered that the pressure from the water is only relevant if the pipe was going thru the bottom.
Now, what would happen if the inlet pipe was place high enough to get the amount of drop/flow needed to the outlet, and that makes it near the water surface level. You get the flow rate that way, but you end up taking the quality water. Put a larger diameter pipe over that inlet back down to near the bottom. The top of that pipe would be seal off, forcing the water to be sucked up from the bottom. I have seen designs like this to remove the bottom water, just can't find an image right now to include here. Hope this make enough sense by description.
Do you think this scenario effects flow rate? Seems like you end up with the best of both worlds: high flow rate and rid of bad water.
