Noisy overflow

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So I've recently got a Aqua One Mini Reef system (120L), link at the bottom. The system seems to work very well however the overflow drain is ridiculously noisy. Like I can hear falling water right now in another room.

The water flows through into the weir and down into the drain as per this picture (1 is down, 4 is return). It's falling into the sump and I believe this is where the noise is coming from. The sump is filled to the specified level.

Can I please have some advise on how to quieten this system.




Well-Known Member
Does the over flow pipe terminate below the water level in the sump or above it? If it's above then that should be your problem. Extend the pipe so that it terminates one or two inches below the water line.

If its already below the water line then there might be too much water being pumped back into the display for the weir to handle without water gurgling on its way back down to the sump. If you have an adjustable return pump I suggest turning it down just a little at a time till the weir can handle the water flow and quiets down. If the pump isn't adjustable find a way to restrict the flow in the return line. I hope this helps and welcome to
It terminates above the sump level. As i'm just running fresh water through the system I might fill the sump up enough so it's submerged. See if that works.

I'll post an updated shortly.
So I've filled the sump up. The water is still very noisy.

You can actually see the water coming out of the drain now. It's hard to describe however it's coming in waves or surges almost as if every couple of seconds more is being pumped or pushed down on top of the usual flow.

I would have thought it should come down evenly?


Well-Known Member
That sounds like the pump is starting to go out on you as it doesn't sound like its pumping consistently. You might consider a new pump.
It's not the pump, it's brand new and output is strong and consistent.

I've been told air hole is big enough in fact it's been suggested that I close it a bit but that had no effect.


Staff member
The single stand pipe design has always been pretty noisy. The gulping effect is usually from too much flow and or not enough air.

You could shove a short piece of air line tubing down the hole on top of the pipe 5-6 inches long. It may help with the gulping effect but flow will still be noisy.

If you want a much quieter system then go for the Herbie set up. Run a external return line for your pump and convert the current return line into a siphon drain with a valve.


Well-Known Member
try removing the top peace to see if the gurgling stops and/or it becomes quieter. If it runs better then you need a larger hole.

The gurgling/surging can also be because the drain ends below the sump water level. So if it was noisy but constant flow before you got the end below the water level, the surges are coming from drain being below the water level.

You might try "teeing" of some of the return so that some of the return is just looped back to the sump. If that quiets things down then the pump is to fast for the drain. Again look at the size of the hole and think about increasing for more air in the drain. Of just let it run at the slower return rate.

Just some thoughts.

Worth at most .02


Staff member
Can I convert this to a Herbie system? if so how?
It wouldn't take much. I'd remove the top elbow that the black, flexible output fittings are connected too on the return line. Then install a valve in that line underneath the stand. It will function as your primary drain. The larger drain will function as the safety back up drain.

Then all you have to do it make a return line for the pump. A little bit of flexible tubing and some pvc is all you need.