I just bought a new boat (to me) and have some head questions.

First some info:

Boat - Hunter 34, 1983

Head - Jabsco manual head

Now my problems and questions:

1. My toilet is filling up with water after it is pumped dry. I am
assuming this is fresh water (lake inlet) but am not usre

2. My holding tank seems to be filling up a lot faster than it should.
I have about a 20 gallon holding tank and it is full after a day sail
with light use. Keep in mind this includes a week's worth of sitting
without use.

3. I'm not familar with one part of the unit...Right next to the head
there is a manual pump. A hose comes in through a thru-hull and does a
loop that wraps back through the pump and to the holding tank. Is this
to pump out of the tank to the lake or the opposite?

Any help would be appreciated.