Replacing black water tank with freshwater tank.

I will find out if my sink goes to BW tank. Yes, I have used a composting toilet for about 3.5 months up in alaska,it worked just fine as long as you divert the urine into a separate container. Used with one other person it for 1.5 months before having to empty it. The waste just comes out looking/smelling of dirt.

My main concern is more about routing new piping from the 2nd FW tank to the sink/bathroom. Would I need a 2nd water pump? Things like that. Thanks everyone for the replies thus far :)