You can drill a small breather hole at the top (through the cap) of the lower section to help drain.
How could a hole that is below the water level inside the mast receiver drain water? Maybe I am misunderstanding something here. Oh, re-reading I guess this comment is directed @ Shelley. I put my mast upright against a wall also, but with the bottom and top up with the parts that slip together down and the water runs right out.
Please comment on this thought ... It seems to me that temperature change as the day cools off is creating a vacuum in my mast resulting in the water being sucked into the mast. I thought that drilling a small breather hole near the top of the mast would eliminate this vacuum (if in fact that is what is happening) thus preventing water from being sucked into the mast.