He talks about how a properly built sump should not flood if the power goes out, and talks about drilling a hole that will become a siphon break so that your tank won't drain into and exceed the volume of your sump.
That's great and all - but what about when the power comes back ON? Now your sump pump is putting water back in your tank, but the siphon is broken, water is not returning to the sump, and your tank overflows.
Surely I'm missing something here, but what is it?
The siphon break hole is on the return. When the pump is turned back on water is pushed up from the pump, fills the tube and out into the tank. When power is turned off unless there is that siphon break hole or the return is close to the surface of the water so air gets into it it will turn into a siphon that empties the tank. You don't want the return to be a siphon, it will become one unless you are aware and take steps to prevent it!