As I was getting ready to leave the boat this past weekend, I went to use the head and found it was not fully operational. It would not pump water from the lake to rinse the head. It would take the waste from the bowl to the holding tank without any problem. I checked the thru-hull and it was not obstructed...thus, I am making the assumption there is a clog or some sort of obstruction between the thru-hull and the bowl. Does anyone have any advice on where/how to check the line to see if there is an obstruction...or has something else failed in the system that I need to check out. Thanks!