Herbie overflow video.

Found this on BRS.
Good video on how to make a silent overflow:

 

...if you have enough space, even HOB overflows can be rigged up in this fashion...

I considered this method when setting up my current DT, but chose instead to use another method, specifically to avoid the use of any valves in the return lines...and yet still control the return feed (overflow) to both the sump and refugium...

 

I might try making a herbie. I have been using durso's with no issues, but my second reserve drain on my 200g is only a standpipe, witha 45 degree fitting on it. If that one gets used, I will definitely hear it. LOL

 

It's extremely difficult to perfectly match your pump. I am using this exact same method to stop the slurping effect. There are a few negatives to using this that I personally found.

1) It's almost impossible to perfectly match your suction with your pump. Eventually it will begin slurping again because it's not exactly matching your pump. Or your tank will overflow if you don't have a backup overflow because it wasen't sucking enough.
2) You loose surface skimming because the suction actually goes underneath the water
3) Tuning it can take hours & is very fiddly/annoying.
4) Can be very unpredictable. Appears to be perfectly matched one day, but the next it's out of whack again. You think it's perfectly matched, but actually it's not because it takes hours to see any results & you end up with water all over your floor

YMMV

C-BuZz

 

I have seen better designs of this method and one of them is to use durso for the backup drain to further reduce additional noise. If in case you cant match it with your pump, only a very small amount of water will be going through the 2nd pipe (durso) as opposed to only using a durso. So if you ask me this method should be more silent nonetheless.
The idea behind this method is to use 2 pipes so you will have a backup one anyway. Ideally, each pipe should be capable of moving all of the flow to avoid overflowing if in case one stopped working.

Not necessarily true. You can do the same for an overflow box (actually building one myself out of acrylic now; having a hard time to get chloroform though lol)

I could say the same about a durso;D;D

Not quite sure about this

 

Agreed. There are many variations/refinements of this system which address all these issues. The video just explains how the concept works.

In general, I'm a huge, flag-waving, kool-aid-drinking fan of the full-siphon overflow. :thumb_up:

 

I've actually come up with a modified version of the Durso that I've had quite a bit of success with that I nicknamed "The Steam Whistle". I'll post a thread of it in the DIY forum once I get internet back at my house. Fried modems plague me. *sigh

 

I tried alot of different things and found out what works best. Place a square piece of Egg Crate large enough to fit and stand over your return entrance opening about 1/4" above and then place a square piece of marineland type Large Cell sponge about 2 inches deep and then on top of this your filter sponge or MICRO FINE CELL sponge to fit snug in the overflow box. NO NOISE. Just a thought. :