Originally Posted by Doodlebug
It normal for a boats to have the battery switch turn off and still have DC power going to the bulge pumps. That would explain why your reading voltage in the bulge water
when the battery switch is off. I wonder what would happen if you disconnected the fuse or wiring? That's assuming the bulge wiring is bypassing the battery switch.
..could also be worth checking to see if there's a small leakage current
on the bilge-switch itself, if part of the wiring to the bilge-switch or pump is partly submerged and insulation
is failing, then it could explain some of the "DC off" losses, in addition to the obvious anode issue.