Brand new contractor installed jacuzzi leaks through 1st floor ceiling. Pulled cover to look. When tub is full, the intake pipe from the tub to the pump leaks through a small hose that is fitted into the 90 degree elbow that runs from the intake to the pump. What is this hose and why would it be leaking water? Backflow? Only happens when I lay in the tub. As soon as I get up and the water level goes down, no leak.. .

Key line for me was "Brand new contractor installed jacuzzi " Call the contractor back and tell him to fix HIS mistake. I would not advise repairing a brand new tub, it should be warrantied and the contractor should warranty his work.