There are three main sources of noise in a tank with overflows and a sump:
1) Water crashing down to the bottom of the overflow box
2) Air/water gurgling in the drain pipe because the pipe is too large
3) Water crashing down into the sump
Number 1 really isn't an issue for you since you're using a hang-on overflow box. You'll get a small bit of noise, but nothing like an internal overflow box where the water crashes 2ft down. Either way, this is an easy fix. Just add a vertical standpipe to raise the water level in the box, so the water doesn't crash down so far. The Durso standpipes are good at this. Dursos really aren't needed for your overflow box, a simple standpipe will take care of the issue.
Number 2 is the hardest problem to solve. While Dursos can address the noise in your overflow box, they do NOTHING for the gurgling in your drain lines. A typical drain has air and water mixed in it. That is what causes the gurgling that sounds like a toilet being constantly flushed. The only way to truly solve this problem is by running a Herbie or Beananimal system. This work be restricting the main drain with a valve, and allowing the water to back up. You're essentially running a full siphon. Full siphons have no air in the line, so it's completely silent. BUT, that restricted drain is no longer handling 100% of the flow, so you need an emergency backup line.
I think you may be able to incorporate a Herbie method with your system. Use one of the lines in your overflow box as the main drain, and put a gate valve on it. This is how you'll control the flow. For the 2nd line, make this one a little bit taller than the other standpipe, but below the lip where the water spills into the box. This will be your emergency standpipe. It may take some creativity, but I think it could work.
Number 3 is also easy to fix. All you need to do is extend the pipe that goes down to your sump a few inches below the water level, or raise the water level in your sump.
Hope that helps!
1) Water crashing down to the bottom of the overflow box
2) Air/water gurgling in the drain pipe because the pipe is too large
3) Water crashing down into the sump
Number 1 really isn't an issue for you since you're using a hang-on overflow box. You'll get a small bit of noise, but nothing like an internal overflow box where the water crashes 2ft down. Either way, this is an easy fix. Just add a vertical standpipe to raise the water level in the box, so the water doesn't crash down so far. The Durso standpipes are good at this. Dursos really aren't needed for your overflow box, a simple standpipe will take care of the issue.
Number 2 is the hardest problem to solve. While Dursos can address the noise in your overflow box, they do NOTHING for the gurgling in your drain lines. A typical drain has air and water mixed in it. That is what causes the gurgling that sounds like a toilet being constantly flushed. The only way to truly solve this problem is by running a Herbie or Beananimal system. This work be restricting the main drain with a valve, and allowing the water to back up. You're essentially running a full siphon. Full siphons have no air in the line, so it's completely silent. BUT, that restricted drain is no longer handling 100% of the flow, so you need an emergency backup line.
I think you may be able to incorporate a Herbie method with your system. Use one of the lines in your overflow box as the main drain, and put a gate valve on it. This is how you'll control the flow. For the 2nd line, make this one a little bit taller than the other standpipe, but below the lip where the water spills into the box. This will be your emergency standpipe. It may take some creativity, but I think it could work.
Number 3 is also easy to fix. All you need to do is extend the pipe that goes down to your sump a few inches below the water level, or raise the water level in your sump.
Hope that helps!
lol
