My only thought on the returns, were not the length, but based on how they were pointed and the water flow, one overflow was forced to try to take on more water than the other. But I think you said that they were essentially pointed equally across the tank?
What do you mean by "louder return line"? I know one drain can be louder (usually attributed to sucking in air). But is one return line creating more noise from water?
On the durso - does it have the air tube at the top with any valve adjustment for air?
When i say louder i guess i am referring back to my original post. The right overflow, when looking from behind, will suck water down loudly past the set point of the overflow, it will then fill back up again to the set point and then suck it down lower again, rinse and repeat
Is it possible that the air vent in the top of the durso has become blocked? It sounds as if the water level is getting so high that it's starting a siphon and then sucking the water level down until the siphon breaks at the overflow inlet.
Is it possible that the air vent in the top of the durso has become blocked? It sounds as if the water level is getting so high that it's starting a siphon and then sucking the water level down until the siphon breaks at the overflow inlet.
I was thinking along these lines so was wondering about the valve on the durso.
Sometimes i wish we were all MFK neighbors, as it would be much easier to walk over and troubleshoot rather than ask the 101 questions that I do. Just my nature. Knowing it may lead nowhere lol.
Then again I'd get no real work done. OP assuming you check any durso blocks, have you checked the air valve as mentioned? The sucking in air will definetely cause the noise.
Maybe we should all just pick a city and move there. Lol