There are 2 through hull fittings with ball valve shut-offs in my head. One supplies the toilet but I'm not sure what the other one supplies. Both have the same size hoses but the one I can't figure out disappears through the rear bulkhead in the head. It could be for the raw water pump for engine cooling but there is no filtering device over the through hull to keep "stuff" from being sucked through the raw water pump. Any ideas?