it is a 12x18x52 metal side pool with a 16" 100lb sand filter with a 1 hp 2600gph pump. the foam i was thinking of using is ridged and is ment for burial under concrete slabs and is rated at 25psi. if there is a better product i am open to suggestions. i am tring to aviod sand as my water table is high and im afraid of the sand washing out.