Ah yes...b----y marine
We recently found both our 'guest' (portside) heads blocked. We then found many sympathetic shaking heads, happy to watch from a distance
as we searched for a solution. Eventually, after a half-day almost literally bathed in s---, both heads were restored to full operation.
All of our heads are Jabsco
electric flush heads with what are described in the manual -- see attached
pic -- as "joker
" valves; these valves appear designed to stop inappropriate matter, e.g.
, from flowing into the pipes. Given their function, perhaps they were meant to be called 'choker' valves...or else, as it was for us on that fateful day, the valves that can end up saying 'The joke's on you'!
Anyway, they may also be exactly the valves DavefromNZ describes as non-return valves.
After much searching, we found that both of our blockages resulted from the combination of the joker valves and not flushing
the toilets for long enough. If the toilet is not continuously flushed until the matter is all the way into the holding tanks, as soon as the flush pressure stops the matter will flow with gravity. Gravity will then often take the matter back up against the joker valve from the other side, eventually causing the joker valve to be blocked...and so it was for both of our blockages.
So our important observation (and Rule #1 for guests on board) is...BE SURE TO FLUSH FOR LONG ENOUGH TO RUN THE MATTER ALL THE WAY INTO THE HOLDING TANKS.
From some heads, there is quite a length of tubing between the head
and the tank.
for long enough may (?) also be the cause of matter returning to the toilet, as described by DavefromNZ.
As for the smell, if it's a 'rotten egg' smell, it is very likely nothing to do with what flows out of the head
...and rather to do with calcification around the inside of the INtake tubing. So if it's a rotten egg smell, try just replacing the intake tubes...and that should be rid of it!