If you are using a 1.5" bulkhead you don't need to go up to or reduce in size at all. As long as there is a bend in the line heading to your sump that will create the backpressure necessary to keep the durso quiet. I had a 1 1/4 reducer in my durso from a 1.5 bulkhead and took it out to see if it operated differently when I was testing my ampmaster3K. No change.
If you are running a smaller bulkhead the reduction is necssary. All you will do by adding in the reduction after the bulkhead is reduce the max flow of your durso. In this case.
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Darren
Always strive for the optimum environment, not the minimum environment
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