Customer has 3 y/o Rheem heat pump system that operates for upper level. System was not cooling due to water in pan. Removed water from pan. Noticed that main and upper level systems are sharing drain line. Clog in drain line due to improper pitch. Cleared drain line and p-trap for both systems. Relocated drain lines for proper pitch. Tested systems. Pressure levels were normal. Replaced 16x20x1 filter for upper level. Systems are currently working.