Help sucking vortex.


Premium Member
Just water tested my new tank setup. Good news Squirt and Eheim 1260 are working great. Bad news I get a sucking vortex in the overflow then the water levels drops and a surge flows through the sump. If I use the ball valve and slow the flow down everything works, no noise and constant water level in overflow.

Overflow is a 17" horizontal box at the top of the tank with a 1" drain drilled through back of tank. A 90 degree elbow facing down connects from the overflow into the bulkhead then a 90 degree out of the bulkhead. Half way down it's got a 45 degree elbow.

Return pump is a Mag 7 connected to 3/4 inch pipe. It's pushing a 3.5 foot head with one 90 degree elbow and a ball valve. It exits from a Y into two outlets.

Tried drilling holes in top of the drain's 90, even fed an air tube down the pipe. They didn't help. The head loss calculator say I'm pumping 435-450 gph and a 1" drain can handle up to 600 gph.

Do I have to much flow or do I need to somehow change the drain configuration?

i have 1300 gal/hr running into my tank wit a 1"pipe return and quiet. drilled a hole on top of return to stop the noise. I think if i'm reading your thread right that you have a 90 degree elbow for your return. i used 2- 1 1/4" 90 degree making it 180 degrees and adding a hole to stop syphoning noise. it's almost undetectable as far as noise.
by the way i added a air line tubing length about 8 inches in the hole and the noise is nonexistent
I'm doing the exact same thing. I've built an external durso stand pipe that I hope will work. Haven't tested it out yet.
I have a 1" 90 street ell in the inside of the tank, on the outside bulkhead a 1" T with a cap on the top that will have a small hole. Should work for your application as well.
Go to and build your own standpipe. Will give you everything you need.

Good luck!
I have found that the angle of the drainpipe can make a huge difference. I have a basement sump that I'm wet testing now. Very small changes to the angle and position of the drainpipe into the sump would eliminate the flushing I was getting from my durso standpipe running about 1000gph.

I'm not entirely sure what all the factors are causing the 'burping' but it's a combo of flow, horizontal and/or vertical runs in the drainpipe along with how submurged the pipe end is in the sump. The factors are are sorta interrelated.
Thanks for the help.

I think I have it now. Went with the 1" 90 in the tank and 1.25" T and drain pipe outside.