Why do pool deck slabs sink more than other concrete around the house?

Pool decks are surrounded by water-saturated conditions from pool splashing, backwash discharge, rain runoff, and often a high water table near in-ground pools. Sandy or silty soils backfilled around the pool shell during installation are particularly prone to washing out over time. The combination of saturated soil and repeated wet and dry cycles makes pool deck settlement one of the most common concrete leveling scenarios.