If water pressure from the tap will "pop" the mast apart it'll be tight enough to separate by hand! BTW, if you've ever tried to pull off a cap from an Artline marker pen you'll find that twisting is much quicker and less effort rquired to remove the cap. So are mast pieces, twist is best!
So with this thought, first bit of kit are dishwashing gloves with two people and twist apart from either end. If that fails inner tube wrapped around one side of the join and then a wet towel over that wound on tight like a tornique (sp?) with a length of anything eg. mast extension, don't overtighten! One person holds the mass of tight towel and the other with rubber gloves grabs the other end and twists the mast apart. The trapped sand will grind a nice little spiral on the stubby bit of your mast.
If that method fails sell me your mast bag coz you have created a one-piece mast like the old days and won't be able to use the bag.

It was so much simpler...and cheaper then.