Peggy, I am installing a holding tank in sailboat and would like to know how to locate where to install the tank vent. The easiest location is on the port hull near the tank. However, when the boat is heeling the vent be below the waterline. Can I install a scupper valve, or do I need to run a line aft? If so, how far can I run a vent hose? The longer the hose run, the harder it is to avoid low points. Also, as you advise in your book, I am installing a vented loop in the seawater inlet between the pump and the bowl. Can I tie the vent hose from the top of the loop to the holding tank vent? This would save me from adding an additional thru hull, but I am concerned that odor from the tank my find its way to the bowl when I pump the bowl down. Thanks for your help. VR, Dave