Fuck sake that was a hard read. That poor mother. I can’t even comprehend the purpose of that pipe. They describe it as a lazy river so I’m assuming it’s some sort of equalizer pipe to the other side. Water flows in one direction around the pool and I think what they’re saying is the flow of the river was reversed for whatever reason. There would be quite a strong amount of suction through there, even if it wasn’t a direct intake line to the pump.