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Anti siphon dead ends in bilge

Jun 30, 2021
Catalina C30 St.Clair Shores
Hello there. I recently purchased a 1985 Catalina 30. Going through the systems I am a little stumped. My exhaust anti siphon is set up unlike anything else I have seen in my searching. The line from the heat exchanger as well as the line that goes into the exhaust elbow. Are both routed into one end of the anti siphon U bend. They are together entering the same end of the tube. On the other end is a larger hose. Maybe 3/4" I.D. the end of this just terminates and is laying in the bilge. Can anyone please explain why someone might have done this. I can't find a single thing that would make sense of it. She is still on the hard. But it seems that water from the exhaust would just be constantly draining into the bilge. Instead of cycling all the way through the actual exhaust system.
Jun 30, 2021
Catalina C30 St.Clair Shores
sorry, it is a universal M25. I will post some pictures when I get out to her this weekend. But would really appreciate any help.
Nov 6, 2006
Hunter 34 Mandeville Louisiana
Sounds screwy.. Seawater should go from the heat exchanger through the anti-siphon loop, then into the exhaust elbow; the siphon break should be in the line between the heatex and the elbow.


Oct 21, 2009
hunter 38 Monaco
The anti siphon is always leaking a little bit. I found the same situation on my H38 many years ago. The salt water leaking from the exhaust elbow anti-siphon entered a thin hose that was just stuffed away so that the water leaking ends up in the boat bilge. I let it finish in an empty water bottle that I empty when full.