Drain noise - one Durso "flushing" - other isn`t?

Looking for some advice as I have a 120g RR with two stock Durso's - right side is perfect and left side is flushing periodically.


Pictures below - length for the right side (quiet) is substantially longer which may have an impact. Initially both returns were about 1.5" below the water surface. I changed the noisy side to .5" below, out of the water and 2" below which no real change.


I read on the Durso FAQ's that this is almost always caused by back pressure in the drain.


My next step is to go into a 1" Tee (vertical) on the noisy return and install a riser for a vent - possibly with a cap and vent hole for a reverse Durso.


Thoughts?


Thanks!


-Eric


Left (noisy) with changing water level (approx 1"/DesktopModules/ActiveForums/themes/_default/emoticons/wink.gif





Right (quiet and stable)

 

The dursos have a hole in the cap ( 1/4"? ) with a semi-rigid piece of tubing sticking out of it.


-Eric

 

That's a great idea!


-Eric

 

They're both close to 90 degrees. The way the bulkheads are (slip vs thread) I didn't have opportunity to experiment. I do have the ability to go to a 45 degree if needed.


-Eric

 

Tried that and it didn't seem to matter. I would like to mellow the flow into the sump as it's full of bubbles.


-Eric

 

Thanks for the responses!


As I mentioned (later, not in the 1st post) the Dursos have a vent hole drilled in them already.


I replaced the 90 deg into the sump with a vertical "T", added a 2" PVC scrap and a PVC cap. 3 small holes in the cap seem to have stabilized the return.


Although I no longer have the flushing, 2 issues still persist:


[list type=decimal]
[*]The overflow is quiet but I can still hear some turbulence/gurgling in the PVC so the issue isn't 100% resolved
[*]The drain into the sump is creating quite a bit of bubbles (though fairly quiet) that's allowing micro bubbles into the display
[/list type=decimal]

I've been reading about using spa flex or just flexible hose (similar to what OEM's use for sumps) and can get both at Theisens to reduce the noise as well as going to 45's instead of 90's.


Would also like to reduce the bubbles in the sump but I'm thinking that by reducing the trapped air in the drain I'll reduce the turbulence in the sump.


-Eric