Upgrade time !

[gregzz4]

Originally Posted by Craigdillman

It seems that the noise is mostly coming from the water falling into the overflow not slurping or gurgling from the pipes

Because of a lack of drop between my tank and sump, I don't use my drain valve to dial in anything. Instead, I have to dial back my pump with an 'exhaust' tee back to the sump. But it's the same principal

My overflow is very quiet
I currently have my main drain standing at around 5" below my overflow teeth, my emerg drain between 1/2" and 1" from flooding (haven't measured it), and I run my overflow box level within an inch of the emerg height. It fluctuates some, but never gets my emerg plumbing wet. And I like it that way as I have horizontal runs to my sump so don't want any stagnant water. Nor do I want a constant slow trickle. I've done it this way for nearly 18 months and am happy with it
I don't even have to adjust the valve anymore

For you, once you find the heights you like for your pipes and water level, I'd suggest you dial in your system to run your pump full out
Then just live with the overflow teeth noises when you dial it down