My parents have a happy and healthy grapefruit tree, so far this year it has produced over 200 grapefruit. They donated 150 to st. vincent de paul, a food pantry my mom volunteers for and still had a bunch left over. Of course, I asked for some and they brought me 2 grocery bags full. So I juiced them, well my husband and I did. You don't need a fancy juicer, all you need is a hand held juicer (the yellow thing in the photo) and a pitcher (and a knife).
Cut grape fruit in half and then in half again.
Make sure the juicer is in the pitcher, otherwise juice will shoot out everywhere.