Due to a recent storm in the area, a felled tree knocked over a potted plant which crashed into the PVC piping for the filter and pump. While replacing the piping, I noticed that of the three valves, two were closed and one was partially open.

As I'm new to taking care of my pool by myself, I was wondering where the pipes go to, and what the valves are there for.

For the record, there are four pipes coming from the ground. One must be from the pool and leads to the pump, and then there is a pipe from the pump to the filter. Then there is another pipe from the filter to the three pipes in the ground. I'm assuming there is only one intake pipe, and that is the one leading to the pump. The other three must be for output. I'm also assuming that one pipe is for the aerator for the pool (maybe the thinnest one that is closed off by the valve) and the largest one that is partially open must be going back to the pool. Any idea what the other one is for? There are no water features for the pool. Could this possible be waste and lead to the sewer? The diameter of the PVC is from left to right in the picture, 3/4'' PVC, 1 1/4'' PVC, and 1 1/2" PVC, all leading to 1 1/2'' PVC that connects them to the filter.

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