Water flows through overflow box hidden under the deck. The is no obstructing grates in yuor view, all are hidden underneath the deck. You can utilize the use of space up to the pool. Balance tank is required in the hidden flow system. Hidden flow system is customer’s choice of the system; we built, built more hidden flow type than all other systems combined. Hidden flow system enables to built under deck wall wash LED lighting, semi automatic integrated pool cover No other system gives mor choice than hiddenflow system, Please view animation and our gallery for further information.. One more; We can apply all surface covers (PVC liner, glass tile, ceramic tile, granite tile etc) on FLEXPOOL hidden flow system..