My model according to manual drains to sink. After I posted this question I went to Catalina Direct and they make a repair kit and say the rubber wears out and to replace every 3 to 4 years. To my knowledge mine hasn’t been touched. I also learned that it pumps out on both storks...
My 97 Catalina 30 MK lll just started siphoning water into refrigerator box. I can’t find a check valve in the drain system to sink. My guess is that the foot pump is supposed to do this but mine isn’t working anymore. The pump works!