In your pool pump/filter area you should have two sets of jandy valves (hopefully labelled). One set is for your pool intakes and leads into the pump. Another set is for the pressure side (pool returns, jets, etc). You should be able to partially close the valve to the main drain on the suction side, though it would be wise to also make sure any other suction ports are all the way open (skimmers, spa drain, etc)
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