[sawdustdad]

The first gray water pump is on top of the gray water tank, the second is a rule bilge pump inside the tank. On my 3700, the gray water tank does NOT go to the head holding tank, it goes overboard.

Your head sink, shower, floor drain, and cabin A/C condensates all go to the forward bilge sump which pumps to the gray water tank. The galley sink goes overboard. The bridgedeck sink and under seat storage/gear locker drains go to the gray water sump. Gray water goes overboard. I plumbed my bridge enclosure A/C unit condensate drains to the gray water tank as well to reduce the number of thru hulls.

All of this is in the owner's manual. If you don't have one, call Tiara, they will email you one!