I am by no means an expert, but thought I would share my experience with the herbie. I found that if your return is adjusted so you get a smooth flow over your overflow it is quite easy to adjust the gate valve to give you a nearly silent tank. I have the sump under the tank, with the tank in the living room. The loudest noise is the hum of the skimmer, second loudest there return pump (a speedwave), and finally there is an slight water trickle noise as the water flows into the filter socks. The drain itself is silent. As the others have mentioned I have it set so a very small trickle goes into the second drain. This makes sense to me as either the main drain is adjusted absolutely perfectly so the level never changes, or the level in the overflow slowly rises or falls. If you set it so it slowly falls, you will get a lot of noise once you get the water spout. If it slowly rises, the second drain takes the very slight trickle quietly as it pours right down the inside of the pipe. I can turn the return off and not once had to readjust the gate once the return pump is started.
So the advantages I have found are silence, ease of operation, and no bubbles in the sump.
- Ian
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