I am fed up with trying to figure out ways to keep the pigs from spilling or muddying their water so I want to go over to nipple waterers fed from a 55gal plastic drum. Who sells good adjustable gravity flow swine nipples? I'm planning on putting them at three different heights - 12, 14, and 16 inches or is this too close together? My thinking is they'll move up to the higher nipples as they grow. They're in the forty pound range now. Thanks.