I have a 4200gph pump with 2 discharge lines. I was thinking about using 2 of these spillways for a pondless waterfall. Will I run into problems?

I designed a pondless waterfall using two Aquascape waterfall spillways to give me a split level two source waterfall. My "pondless" water reservoir at the bottom is 3'x7'x4' deep. I have a 9000gph Aquascape pump with a single line 4" hose that pumps the water to the top that has a 5' rise. I have a splitter at the top that runs the 4" hoses to the two spillways. I have had this waterfall setup for 4 years having the waterfall run 24/7 from Spring to Fall. These spillways have been maintenance free with a natural looking waterfall flow from the two spillways. These spillways work exactly as they are advertised without an ounce of problems or disappointment. Two unrelated suggestions is to: make sure you remove your pump before winter, clean and brush off any rust, and then coat the exterior with grease and store in your basement. Second, avoid filling your "pondless" reservoir with a lot of rock or stones. Fill the reservoir with the plastic crates and then cover with a heavy plastic netting to limit debris from going into the reservoir. This will make much easier to clean out the reservoir both when you winterize it and when you want to clean it in Spring to start it up again.

I have 1.25” tubing, what do I need to make this work? Thanks

Please take the 1.25 tubing back to where it was purchased and pick up 1.5 spiral kink free or 2 inch PVC flex. This will ensure you get the full amount of flow from your pump to the spillway without restricting the flow due to friction loss. Undersize tubing is what most often results in consumers being dissatisfied with their water features or why they blame the pump for not delivering the flow it is rated at. YES, you can rig that size tubing to hook up using a 1.25 barb adapter but would not suggest it unless absolutely necessary