if you want your sump pit to fill up with sand
go ahead and use it...
I suggest you jsut put marble sized gravel around
then either take a drill and drill a lot of holes through
the top half of this pit to let the water come through it...
I have also used a skil saw and cut slits through
the palstic before ,,,,, long cuts all throughout
the top half of the pit works great to let the water
come through b ut not the gravel
sand will simply find its way through