I have a Jabsco quite flush head.
The quite flush is 6 years old and the joker valve had not been changed. I decided to do some preventive maintenance and change it with a new one. Now the bowl will not hold water, it goes down to the bottom leaving maybe an inch of water, this happens within a minute. before it would hold a third of a bowl for weeks. Any suggestions?
Part #16 in a Jabsco manual toilet has nothing to do with it, neither does any vented loop. Except for the high end electric toilets with multiple flush options which include adding water to the bowl ahead of solids, marine toilets aren't designed to hold water in the bowl.
Your bowls only held water because water runs downhill and your joker valves were worn out...so any water left in a line that runs even slightly UPhill from the toilet will run back DOWNhill into the bowl when the joker valve becomes worn enough to prevent the slit from closing tightly behind each flush. At first it's just slow seepage, but in time the joker valve will become so worn that the slit becomes a hole that can no longer block any backflow.
In electric toilets, the joker valve is only supposed to block a flood into the bowl, which it can't do if it's worn out. But that's the least of what the joker valve does in a manual toilet...it's the single most important replaceable part...and it's essential that it be replaced at least annually Find the article "joker valve 101" in the archives for this forum for the complete explanation (it's also in my new book).
Joker valves in electric toilets should also be replaced annually or at least every two years if you don't want water from the toilet splashed all over the head when you heel. Use a cup from the sink to add water to the bowl ahead of solids.
