I've been wondering, but haven't fiddled with it enough at what percent the humming would stop. Went down to 80% and that seemed to do the trick. What did you end up replacing your flow nozzle with? Looks like an AI Orbit Cross-Flow?I now have the return set to 70% to minimize the humming sound of the return pump while maintaining a completely silent flow thru the filter roller.
So happy with the way things turned out.