The eastward flow of the Equatorial Counter-Current (ECC) is primarily driven by the accumulation of water on the western sides of ocean basins.

1. The North and South Equatorial Currents are driven westward by the Trade Winds, causing water to 'pile up' against the western shores (e.g., the western Pacific or western Atlantic).
2. This accumulation creates a higher sea level in the west compared to the east, resulting in a pressure gradient.
3. In the zone between these two westward currents (the Doldrums), where surface winds are weak, this accumulated water flows back eastward under the influence of gravity to restore the ocean's equilibrium.
4. While the convergence of the two equatorial currents leads to this 'piling up' and subsequent downwelling (sinking of water), the resulting pressure gradient is what facilitates the eastward return flow known as the Equatorial Counter-Current.