Last weekend the head would not pump well. Intake is only a 1/2" opening and I am docked cross-wise in a river so all kinds of stuff hits the side of the boat and sometimes parks there (reeds, other plant matter for example). Toilet pumping very hard, pulled out the Jabsco filter screen (yes, you absolutely need one of those to protect your toilet!) and it had some black rice like stuff in it, but cleaning did not improve pumping action much, so I went swimming with a rat tail file to clean out the intake. Must have dislodged something nasty as now the toilet did not pump at all!!! Pulled the hose off the intake valve, wife flushed quick on and off, removed filter screen again and cleaned inside of filter housing where I found a little ball of mung, yep almost exactly 1/2" diameter. Never a dull moment. Nice safe docking on a river (no wave action, safe in big storms), but not a clean set up for the toilet.