OK, OK... I will answer your ? and just ignore everyone else. LOL...
As seen buy the responses, there are many ways to skin a cat, but only one way to skin a saber toothed @BeanAnimal.
The first two pipes in a Bean or Herbie are the same. The first being the lowest one in the overflow, I run one with a strainer, but not required. That runs directly into your mechanical filtration device. The second pipe which will be higher than the main (first). This is where I run my water level at, just trickling over the edge. I run the second pipe submerged into the sump. You can choose the run this into your mechanical filtration or fuge or wherever. These two pipes alone will be a silent system. The Bean animal has a third E-drain which separates the two systems. This third pipe, which sits higher than the first two, is a true emergency drain. It should never see water. Even when the pumps start after feeding and the first pipe has not started a full siphon, the second pipe should be able to take the overflow. The third pipe should discharge into your sump above the water level as a noise indicator. Now as some have posted previously, the noise (air suck) should be louder than any waterfall noise into your sump. This may be the case on some instances but not all, and probably not most. For example, under normal running conditions as described above (slight trickle into pipe two). Lets say a snail completely blocks pipe two. Your water will rise until it just trickles over your third drain. If your third drain is submerged, you will never know the difference, it may be months or never. If there is a catastrophic failure in both drains one and two, than yes, it will create a big sucking noise.
You could also run a level indicator in your overflow attached to a controller to sound an alarm or use a simple cork in a tube on a stick to indicate the water level in your overflow.
-T
As seen buy the responses, there are many ways to skin a cat, but only one way to skin a saber toothed @BeanAnimal.
The first two pipes in a Bean or Herbie are the same. The first being the lowest one in the overflow, I run one with a strainer, but not required. That runs directly into your mechanical filtration device. The second pipe which will be higher than the main (first). This is where I run my water level at, just trickling over the edge. I run the second pipe submerged into the sump. You can choose the run this into your mechanical filtration or fuge or wherever. These two pipes alone will be a silent system. The Bean animal has a third E-drain which separates the two systems. This third pipe, which sits higher than the first two, is a true emergency drain. It should never see water. Even when the pumps start after feeding and the first pipe has not started a full siphon, the second pipe should be able to take the overflow. The third pipe should discharge into your sump above the water level as a noise indicator. Now as some have posted previously, the noise (air suck) should be louder than any waterfall noise into your sump. This may be the case on some instances but not all, and probably not most. For example, under normal running conditions as described above (slight trickle into pipe two). Lets say a snail completely blocks pipe two. Your water will rise until it just trickles over your third drain. If your third drain is submerged, you will never know the difference, it may be months or never. If there is a catastrophic failure in both drains one and two, than yes, it will create a big sucking noise.
You could also run a level indicator in your overflow attached to a controller to sound an alarm or use a simple cork in a tube on a stick to indicate the water level in your overflow.
-T