Peggy, A note of thanks,for the ideas and methods for implementing them. I now have an insection port on the top of the holding tank where none was before. The rest of the project of replacing ALL hoses into and out of the holding tank is underway ( the boat is on the hard for the winter) and there is now a vented loop between the pump and the toilet. I just read the Y-valve thread and will be disconnecting the Y-valve and removing the hose to the waste discharge thru-hull. I am a Great Lakes sailor. thanks again, Tom Ehmke Tom