Water stains on maple are often only superficial and sand off readily. Some floor installers recommend using chlorine bleach, oxalic crystals, acetone or lacquer thinner to remove water stains, but utilizing these products can exacerbate the issue. Sanding water stains to eliminate them results in a new, consistent surface for applying stain and lacquer. Even in case you don’t have stains on your maple, sanding is a good idea.
Lay the maple floors on a worktable surface one bit at a time. Using 100-grit sandpaper attached to a hand block or a oscillating tool with a sanding attachment, start sanding from 1 end.
Sand with a moderate amount of pressure, moving forwards 4 inches at a time, and then back 3 inches. Constantly sand parallel to the wood grain. Never allow the sander to bend across the grain.
Apply more pressure to stained areas, sanding in 1 place till it disappears. Keep moving forward until you arrive at the end of the board. To complete each plank, sand ahead and back with long strokes 24 inches in length.
Dust off the plank with a soft fabric. Hold the board up at an angle that light reflects off the surface of the plank. Start looking for scratches, and rough or uneven spots. Start looking for further stains or discolored areas. Should you find some of these, resand the plank. Check again and resand if necessary.