Help with overflow

[waterloomarc]

I'm still trying to get my overflow to work properly (quietly). It is a back driled tank, about 4 inches from the top. There is an elbow and a short piece of pipe rising to the top of the water where it is capped. The riser pipe has holes drilled around the side to allow the water to enter the overflow. On the back outside of the tank there is a Tee, similar to the Durso. I've placed a hole in the top of the tee to allow for air.

My problem is this, the water level isn't steady in the tank. It rises, at which point there is a lot of air in the water travelling to the sump (very loud). After a certain amount of rising, a syphon is created (quiet) and this causes the water level to fall until the holes in the pipe are exposed to air breaking the syphon. Then it starts all over again. What am I doing wrong? Other than not buying a reef ready tank to begin with. Is the hole on the tee of the Durso not supposed to regulate the water level and prevent a syphon from occurring?

I apologize for being so lengthy, but I'm at my wits end here and wanted to give you guys enough info to come to my rescue. Also, before I tried this mod. I just had the pipe to the water surface with holes drillled in the cap for surface skimming, but found this allowed too much air in so I switched to what I have now. I guess it's close to the Stockman mod.

Thanks again!!!! Please help me.

[Aragorn]

I had the exact same situation when I built my Durso. I solved the problem by enlarging the hole at the top of the tee. Try that, should work. HTH

[waterloomarc]

I don't know how much more I can enlarge it though. It's already at about 3/16"

How large did you have to make yours? I appreciate your help!!

-Marc

[Aragorn]

I enlarged mine by putting in multiple holes of about 3/16". I had to drill 4 of them in fact before my Durso "settled down" and became quiet and stable. I would recommend either enlarging it slowly or drilling another hole, see if your overflow stabilizes and repeat if need be. HTH