[robert]

Don’t bother with “T”. “T” will not remove the noise, or the bubbles. It works only as muffler. In order to make an overflow totally silent all the way through, you have to change the free water fall to the siphon. One way of doing this is to attach the gate valve where the water enters your sump to restrict the flow a bit. I alos got rid of durso and replaced it with “U” shaped PVC tube. One end connects to the overflow pipe and other end has a pipe on it with original strainer that goes about half way down inside of the overflow box (see drawing below). What is also important that, the top of the “U” tube is well below the top edge of overflow box teeth, below the bottom edge is even better (my setup). I just adjusted the gate valve to find the sweet spot to keep siphon going without overflowing the tank. Since I am paranoid, I attached my return pump to a simple float switch (via relay) that would turn the pump off in case the overflow gets clogged. This modification might look a bit complicated, but totally eliminated the noise and bubbles in my overflow system.