I ran a dedicated DCP3500 pump turned down to 30% on my scrubber and DCP10000 for the return. Since the scrubber doesn’t require a lot of flow I’d give your DCP15000 to your manifold and see where you have the pump set at. I typically buy a size or two larger return pump and run at a lower voltage. If you find you’re looking for more there is the 18000 and 20000.