Silent bends on plumbing

Nothing. Reason being the whole overflow pipe is filled with water from the bottom of the pipe to the top of the overflow. Its like a flow controlled full siphon.

 

Won't it flood?

 

That’s what is bothering me as well..

 

Look at a Dursot standpipe. Very quiet. The open part of the draining pipe is under the water line. Used this in my sump.

 

I also see that some designs have 3 pipes so the flow in each pipe is minimal. Also taking away noise.