SEA, welcome to the forum! The pic helps a lot, but there may be more info that would help us. Can you update your signature please with anything else that may apply? For example, do you have a main drain? Any other suction/vacuum ports in the pool? Two skimmers perhaps? You can see my signature as an example as well.
You have the ability to turn the valves to influence both suction and pressure (return to the pool). From the pic it's hard to tell which pipe is for what function. If they are labeled you could tell us which would also help.