Back to work now. Time has come for us to build in the plumbing, now just where to put it all . Some may popo our idea of using PVC /40 for the plumbing , But we have researched and read and asked and researched and read again. It seems this is workable if you have the room . This being a very spacious boat gives us the opportunity to redesign. Below you will see we have dropped in the grey and black water tanks. We added inspection ports to both tanks to see any problem clogs that may arise. I must say I never want to be in the position of having to view what in the black water tank, and im so glad the ports are large , in order for the fit of burts arm. Below the pipes are laid and glued , and we added high density foam board epoxied in to be braces for the tanks to prevent shifting. Now ready to put the floor in and the toilet .