Overflow Slurping Sound

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I have a 36 gallon tank that I drilled. I have a 700 gph overflow box and a 3/4 in bulkhead. I used 3/4 in PVC for the drain line. I bought an Aqueon 1700 pump which is rated for 264-449 gph. When I run the system, the overflow box starts to fill up to just above the bulkhead, and then every few seconds it makes a loud slurping sound as the water level drops back down below the top of the bulkhead is. My understanding is this is due to a syphon happening. I'm looking for suggestions on how to fix this. I've read about the Durso pipe, but I don't know if this is a possibility since from what I've seen most of those seem to be installed with bottom drilled tanks, and my overflow box is pretty small so I don't have much room for pipes in there. I was considering switching to 1 in PVC for the drain line, but I'm not sure if this will do anything since I still have a 3/4 in bulkhead. Any suggestions would be appreciated!


Well-Known Member
You need to restrict the flow from the return pump. Its pumping in more water to the display than the overflow/bulkhead can handle.


New Member
I just dealt with this problem on my120 I just setup. I would use pvc and put a ball valve or gate valve on the drain and slow it down. I found if I allowed my skimmer box to fill up about half way it got rid of the gurgling