tassod
New member
I believe you have a column of air pocket trapped inside the right drain which keeps water from entering. Until you get rid of the air pocket flow will not occur. Make sure you don't submerse the PVC deeper than 3/4" below surface. Find some way to extract the air from within the PVC and replace with some water. The weight of the water column inside the pipe must overcome the air pocket so the air can be pushed out. Can you temporarily drain the water out above the water level in the sump?
Simon, you are absolutely right. I emptied out the sump like you said and started the pump back and got rid of the air and now its practically silent and the backup is dry! :beer:
here is a video:
http://s1273.beta.photobucket.com/user/tassod/media/IMG_0058_zpsa9a555b2.mp4.html