On the system leading to my Caretaker cleaning system there is a side pipe coming off that has a Jandy valve. It has been in the closed position for as long as I have owned the pool. If I open it so there is flow to both the side pipe and the Caretaker, the cleaning pop up heads are weaker and don't come up all the way, yet I see nothing else happening. The flow port in the pool wall shoots out water whether that side pipe is open or closed. And if I close the side pipe, the heads come up all the way and the jets are stronger. Does anyone know what that pipe does?