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You need to insulate the piping. If you insulate the piping you'll isolate the colder pipe from the warmer moist air that's the source of the condensation.
Foam pipe insulation not spray foam is best but you can also us a pipe wrap insulation
Note: the link to the foam pipe insulation is for illustration purposes only. The item pictured is too small. You may need to go to a plumbing supply house for insulation to cover you're (probably) 1 1/2" (nominal) PVC.