I've given up on the Durso ... too much fiddling, and I need to adjust it whenever something change - eg my prefilter getting clogged.
I've switched to a 2 standpipe system originally described in ReefCentral. ... quiet & easy to operate. This is a writeup:
BeanAnimal's Bar and Grill - Silent and Fail-Safe Overflow System
He used 3 standpipe, but that is overkill. I only have 1 emergency as per the original design.
80 gal FW with 30 gal DIY wet/dry/sump.
9 fancy golds, 1 hillstream loaches, 1 rubber-lip pleco (C. thomasi), 3 SAEs, small school of white cloud minnows, planted.