The automatic water setup I picture here costs about $40 to setup, including the price of all parts and the supply hose.
The picture above is a sow drinking out of an automatic waterer installed in a wood fence post on the edge of their pasture. To put it in I drilled a hole in the post and then inserted it through, securing it with plumbers tape on the outside of the post.
Here's a closeup of the valve. The pigs get water by chewing or licking the valve. They get pretty good at it pretty quickly, using their tongues to trip the valve for a squirt of water, and then swallowing and repeating.
To teach a pig how to use this I just wedge a little wood chip into the valve so that it leaks a little water, and they'll come and lick it, knocking the wood chip out eventually. If they're thirsty, they'll keep at it until they figure it out, and then that pig will teach all the other pigs by example.
The "hood" on the valve prevents the animals from knocking the valve out by contact. Pigs get pretty big, and when a 400lb animal casually pushes, you want there to be some resistance. The unhooded valves can be used for sheep or goats.
The valve is to the right, then a 1/2" galvanize pipe coupling, and then a galvanized "nipple" -- the term for a short length of pipe. The length of the pipe you attach it to depends on how big your posts are. I use a 12" nipple so that I have plenty of room. I drill a 1.5" hole to push this through the post.
I put a 90 degree elbow and another 12" nipple on it to prevent the animals from pulling the assembly through the post. Pigs love hoses and if they can get to them they'll tear them apart in glee.
I assemble this using a pipe wrench and a crescent wrench. I'll wrap the threads of the mouthpiece with teflon tape to prevent leaks, but I won't wrap the threads of the galvanized; it doesn't seem to leak for me, so i skip that step with the pipe itself.
I haven't shown a picture of the fitting that goes from 1/2" galvanized pipe to 3/4" hose thread, but you'll find them in any large hardware store. When I do this sort of project I lay it out on the floor at the store and make sure I've got all the parts.