Remove the window well form, following the manufacturer's instructions. Set it aside.
Excavate the dirt from the bottom of the window well with a shovel. Locate the primary foundation horizontal weeping tile system. The weeping tile system consists of perforated pipes laid horizontally just below the base of the foundation. They are laid on top of a gravel bed. They collect water from the sump pump system, lowering the humidity in the basement and lowering the risk of mold formation. Tying a length of weeping tile pipe from below the windowsill into the horizontal foundation weeping tile system ensures that water from around and in the window well drains away from both the window and the foundation.
Cut into the horizontal weeping tile system pipe at a point directly below the window with a utility knife. Slice the pipe in two pieces and insert a 4-inch T-connection into the cut ends of that pipe, with the long end of the T pointing up toward the surface. The T connection will appear to be an inverted T when looked at from the surface.
Attach a 4-inch-diameter piece of weeping tile to the long end of the T coupling. Run the weeping tile pipe vertically up to a point just below the lower edge of the windowsill.
Recover the horizontal weeping tile pipe with 3/4- to 1-inch of gravel and completely cover the vertical piece of weeping tile. Backfill the hole, covering the gravel with at least 3 inches of soil. Keep the level of soil at least 1 inch below the windowsill.
Replace the window well form, attaching it to the foundation, following the manufacturer's directions.
Add at least 1 foot of 3/4-inch gravel to the bottom of the window well. This will stabilize the vertical weeping tile and help provide continuous drainage along the length of the pipe.