Equipment
Fat Sac
A soft, fillable PVC ballast bag placed in a boat's lockers or floor to add water weight for wakesurfing, named after FatSac, the original and best-known ballast-bag manufacturer.
A fat sac is a flexible ballast bag filled with lake water to add mass to a wake boat. FatSac is the original and most well-known ballast-bag manufacturer in the world and is still made in the USA, and its name has become a generic term for soft ballast. Bags are placed in rear lockers, the bow, or under seats and are filled and drained via plumbed pumps.
Unlike hard tanks, soft bags can be added, removed, or resized to tune weight, but they take up storage and seating space and can develop mildew. Every bag requires a vent or overflow connection; without one the bag will trap air and not fill fully, or it will overfill and grow larger than its compartment, risking damage.