Is there a way to make a pig elevator?

I have a pig spawner, and I want to make a pig grinder that would work like an xp grinder (where you damage the mobs with a fall so the player can kill them with only a punch). In order to do that, I have to drop the pigs 20-some blocks. I started making a water elevator (water and signs alternating), but because pigs are only one block high, when they jump in an air gap they don't reach the next level of water. On top of that, if you make a straight column of water, they only rise up a block or two, they don't rise to the top. Is there any way to make a compact pig elevator?