If your boat's holding T system....
is like the one on my 361, you are correct in noting it is a poor design. I wrote a posting at Peggie's forum that may be of interest to you and other 361 fellow sailors. I described the use of aluminum foil tape to cover the sanitation tubes on my boat, some of which have to remain with unclean water independent of the volume of water you pump into the system. Peggie has raised some corrosion concerns brought up by an “expert” friend, but so far has not come up with any good argument backing his claims. Since I covered the tubes with aluminum, I have been able to increase the time between pumpouts for a crew of three to more than four days, of our 12 Gal tank, by reducing the water volume with each flushing. I did explore for potential locations for a secondary holding tank in our boat but found no good place near the head.
