Hello, still figuring out the plumbing on an inground pool I inherited with a home purchase. In the photos I'll attach I have a waste/backwash line that runs from my filter and exits at the exterior wall from my pool room, where you can then attach a hose or let it just dump. Also directly connected to the waste line is piping that goes into a sub-pump with some I guess which are check valves. Problem is when I try to turn to waste, besides water coming out of the main waste pipe, it also floods the pool room/sub-pump pit. Can anyone tell why someone would plumb this, I can see a sub-pump if something pops in the pool room, but why also run the waste line into it? I'm trying to vacuum the pool to waste and can't do it since the room becomes flooded within a minute. Thanks!
