I recently bought a 2003 Sun Odyssey 43DS and have been doing ALL sorts things over the past year, one issue I noticed was that air was getting in when I turned on the water valve for the main central salon water tank, even just a little while after filling the tank. I tracked the problem down to the "pick up" tube on that tank.
Most tanks draw their water from the bottom but on this water tank its a pick up tube that draws from the top, and as you can see at the junction of the tube to the black plastic screw in part it cracked slightly (I'm not sure how that would happen its in the tank protected from everything but maybe sloshing water).
I tried epoxying and gluing to no avail. Terry at Jeanneau parts has been great trying to track it down, but still nothing and I fear it won't be easily sourceable.
I do think I found a temporary fix though, I broke off the last of the "nub" holding the metal pick up tube and I drilled the hole at the base of the black plastic fitting to enlarge it with a 1/2" drill bit. That allowed for a perfect snug fit with a 3/8" (inside diameter) solid pex tube I got from Home Depot. Just to be sure it stays I put a little 'plastic epoxy' on it. I tested it with my tongue and sucking in to see if there are any leaks and it seems to hold well.
I also made one out of brass 1/2" "nipple" from Home depot. It seems the threads are the same, but I don't like metal threads in plastic screw holes, its too easy to strip the threads of the plastic, also it doesn't have the round "rubber gasket" (above the red tape) that would tightly seal the tank. Without that I believe the water tanks would slowly leak out water when over filling (not a huge deal as only overflow would go out and its only fresh water).
Time will tell - Hope this helps someone else
Tom - Blue Yonder
Editor's note: Edited version based on this original thread at the Jeanneau Owners Forum