John Oppenheimer wrote: My 1985 routes the bilge pump line from the stern through hull through the rear lazarette floor to a strap as high as possible in the rear lazarette, back through the floor, and then to the bilge pump. This raised line keeps water from siphoning back through.
John, I think what you have IS a syphon. If something happens to put your stern discharge below water, and your bilge pump quits in the middle of a discharge, then water will get sucked back into the boat. What you need at the high point in your loop is called a vacuum breaker, it seals on positive pressure (pumping out) but opens on a vacuum <the syphon effect>. Many marine head discharge lines have them for this reason. Jim McEwen (getting ready for the 4th on) Tequila Chica, Dana Point, CA
