Greeting Peggy I am about to launch into a rehab of my waste system on my C27 hull 974 vintage 1973. I have gone through the archives and the notes in the library you have but I guess I still am looking for reassurance. I have bought a rebuild kit for the Jabco toilet and I do not have a problem rebuilding it. My main problem is that the waste tank has only two fittings, an in going hose from the toilet and a pump out fitting from the bottom of the tank to the deck pump out. The tank does not have a “Vent”!! I found this out when the Admiral used the head, pumped it out only to have it come back. I have relieved the pressure and pumped the tank. The tank seems to be about a 3/16th to ¼ fiber type plastic. It is now has bloated shape but does not seem to have any cracks. A guesstamate of how long it has been installed is about eight years with the last five of that having the boat on the hard unused. I was thinking of drilling a hole and mounting a vent line from the outside, sealing and screwing the fitting down. I have not found a fitting yet. There is no large access hole in the tank. Should I install one? Or should I just get a new tank? The last issue is where to put the vent thru-hull. My tank is in the starboard bench just aft of the head (the traditional set up I believe). I have seen where you recommend putting the vent forward in front of where the rail breaks to the bow. Could it go on top of the deck or should it go out the side of the boat? I really appreciate the help you have give everyone and everyone’s participation on this board. It has given me a lot of confidence in working on my boat.