Originally Posted by Mike Canter
There is no back flow check valve in ours and the spray nozzle is located on the side of the tank opposite to the dump valve side
Some of back blow preventer and/or vacuum breaker is REQUIRED on those things.
The standard flusher is, strangly enough, called "The Flusher" and is nothing more than a sprinkler head.. There is no check valve in the head (just the vacuum breaker mounted above the tank.
here is what happens.
When you dump and flush the line is of course full of water. The Vacuum breaker admits air to the line so you get some back flow when you unhook the flush hose, but what you do not see is the line from the Vacuum breaker to "The Flusher" allowing the water in that line to drip into the black tank, Perhaps as much as half a cup, NOTE this is not a problem
BUT then the tank fills, now the pressure in the tank is great enough to force some "Contents" back through the small holes into the body of "The Flusher". and now it's clogged.
I replaced "The Flusher" with a "Tornado" which does a better job of rinsing and which has a spring check in the head. It has not (Several years) clogged.. Nor does it do a better job of spraying down the sensors.
For now, a garden hose held over the toilet while the flush gate is held open, or a bucket dumed down the thing, Every bit as good as "The Flusher"
A Want like the RV twister is better.
The Valterra Master Blaster better still but may not work with your RV.. My home made "Blaster" does.