I had a similar situation, however I turned off the fresh water switch at the panel and that did NOT do the trick. I ALWAYS turn of pump off when away from the boat. I have replaced 11 fresh water pumps in less than 2 years.
VERY GUNSHY!
The head kept filling with water and overflowed all over the head. This unfortunately happened when I was away from the boat. I ended up with 20+ gallons of water in the bilge. There is a valve in the head under the sink that is the problem.You need to take the toilet paper holder unit out to gain access. I took the darn valve apart and found some crap in the diaphram. I carefully cleaned it our and have not had a problem since. Be sure to take a digital picture of the assembly before you take it apart, as the solinoid needs to be in the correct position or you will have bigger problems.
I was a bit miffed that even with the fresh water pressure pump off, a siphon developed and really did a number on the head. When I leave the boat now, I turn the freshwater supply valve off under the floorboard in the galley bilge were my freshwater pump is.
I will be glad to walk you through the cleaning procedure if you would like. I can be reached at 650=465-1501 (cel Pacific Time. I unscrewed the valve from the bulkhead, and found that there are several quick releases on the valve. I then took the unit to the salon table and took it apart. I found a small curly que of white PVC in the diaphram, causing the problem.It was not a 64th of an inch long. I am going to order a back up valve and keep it on board.
After 11 pumps, I keep one of those on board as well. I did go to the 4 GPM pump down from the 5.1 at the suggestion of Sure-Flo.
Good Luck & call if you get frustrated.
Not sure if the problem is in the electrical switch or elseware. I turned the breaker to the water pump off and back on and that seemed to do the trick. This is the second time this has happened. My concern is if someone is not aware, we could have lots of fresh water in the head floor pretty quick. I assume the electric switch goes to a selenoid valve somewhere in the head but not sure where to look. Any ideas?
