Is your overflow really that low in the tank? From the pictures it sits very low. It is usually situated at the top. Maybe something just looks off.
If you have no other choice, put in check valves. Not the cheap kind, they fail regularly. Get a nice Y check valve and put it on the drains and one on your return. This should stop the overflow of water. Will not help if they fail, but better than nothing.
I use them on my return pump to keep from backflow. Has failed, but my sump can handle it anyway.
If you have no other choice, put in check valves. Not the cheap kind, they fail regularly. Get a nice Y check valve and put it on the drains and one on your return. This should stop the overflow of water. Will not help if they fail, but better than nothing.
I use them on my return pump to keep from backflow. Has failed, but my sump can handle it anyway.