Cut off top and bottom of pineapple, then remove the core. Stand upright. Slice downward with a knife along the edge of pineapple to remove skin. Cut pineapple into chunks that fit in juicer.
Cut the ends off of the watermelon and stand it upright. Using a knife, remove the green skin and pith in strips around the melon. Slice the inner fruit into chunks.
Peel mango. slice down center of mango along each side of the pit. Score a grid pattern into fruit with knife. Press the under the outer skin so fruit is pushed out into cubes and scoop them out with a spoon.
Place a cup or juice pitcher under the spout and place a a bowl or pitcher under the spout that dispenses the pulp (if using a compact juicer the pulp may be collected inside the machine).
Turn on machine and begin feeding the pineapple, watermelon, and mango into the chute.
Leave machine on until all juice has been dispensed.
Pour juice into pitcher and add filtered water. Refrigerate for at least 30 minutes.
Pour into glasses, add ice, and garnish with pineapple chunk or a slice of lime.