Sump Drainline Help

Sump Plumbing Expert Needed! I just re-plumbed my 140 gallon with a dorso outflow and am having problems with the air bubbles at the entry into the sump which causes excess noise. I did the same system on another tank and did not have this problem, although it had more of a vertical drop. I have attached a picture which shows the drain pipe with the gate valve above the discharge chamber. The pipe from the valve only extends about an inch below the water surface and I have tried it at different lengths. I did have to have a horizontal section on this one, but I doubt that is the problem. I also had to have the gate valve on an angle instead of straight up and down, so maybe that is my problem? Any experts out there?Attachment 128251

I don't ever understand valves on the drain ? Unless they are for complete shutoff during maintenance the outflow is completely dictated by the pump ..
I use DC pumps which are easily adjusted to only feed the tank so the drain only gets as much as it can handle .
I would try a larger pipe for the outflow also ? All my mega overflows have 1 1/2 out/ drain and 3/4- 1 inch return .
IMO ideally you want the outflow to easily flow through the pipe which a larger one would accommodate better ?

Thanks. I have used a valve on my other tank, even though I have adjustable Varios pumps. Not sure it is necessary, but it seems to work fine. I may try a larger pipe. The Durso standpipe is plenty big, but adapts into a1" bulkhead and then the pipe below is 1". Again though, this has worked fine on my other tank so I think it has to be something with the pipe run that is causing it.

Yea my bulkheads are 1 inch for drain and 3/4 for return also .That is common and expects a flow of 750GPH max .
My tanks have 2 mega overflows so they flow enough for me .
Often lack of pitch or just a slow is what causes the water to pile up and then noise .
How big is your air vent at top of durso ? I have seen some stick rigid airline all the way till out of the bulkhead to help silencing .
How high up in your overflow is the durso ? I keep mine as high as possible to minimize drawing in bubbles .

The air vent size is key. Stand over the elbow top of the durso and drill small holes until the noise goes away.
I’ve don’t that many times with reef setups

The top of the Dorso is 1.25" and it adapts down to 1" at the bulkhead. The Dorso though is fine and doesn't make noise. The noise is coming from the water bubbles exiting the drain pipe in the sum. I think the horizontal section has to be slowing it down somehow and then it speeds up again and creates bubbles? I actually don't really want a lot of flow. I want to maximize the time in the sump.