Sometimes posts do turn up in strange places here if you try to reply to a specific one, I find it annoying but it seems a fact of life and it can be confusing.
I think Jimovonz has hit it, you are over running the supply, it will stop instantly the drive pipe draws in air. With simple valves you may not have a lot of control of the flow, I am not sure what valves you have. Normally altering the stroke of the waste valve will cover a considerable flow range.
If you try to use flow rates too low for the drive pipe size the results are poor so if you have to reduce waste valve size drastically you may need a smaller diameter drive pipe.
If the delivery head is too low you can artificially increase it with a partly closed gate valve in the delivery.
I can get them to run with a delivery head about 3 or 4 times the drive head but that is not with simple plumbing fittings as valves. I must look at jimovonz's magnetic control, I have considered it and my tricks with springs probably does exactly the same thing. With decent valves and sufficient control you can get away with lower drive heads and lower ratios of delivery to drive. With simple non adjustable valves you have more constraints.
Sort out your water use and you should be ok.
Flux
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