Pool Plant Schematic

Hello Whilst drawing out the schematic I found a pipe and a pump which I cannot identify. The pipe comes off the main circuit just after the filters and runs vertically up the wall to a smallish pump. After the pump the pipe continues vertically up the wall before disappearing into the wall near the ceiling. There are no flow direction arrows on the pipework so I do not know if the pipe delivers water to the system or removes it. There is a ball valve where the pipe joins the main circuit which is currently closed. The pool is currently shut down and there is no one who knows the system that I can ask. I am due to re-start the pool operation once I have completed this training. Do you have any ideas what this pipe and pump do? I have photos that I can send if that helps. Thanks Ben Miller