Just thought I would drop in and share my experience of putting in a tire water tank. It was a very good experience. I have had it in for awhile now and it is working excellent. The tire I used is very large and heavy. It is roughly 7 ft across and 30 or more inches tall. I got it for free from the local ag tire store in town. It was a large scraper tire and perfect for what I was looking for. Although weighing in at 1200 or so lbs its perfect. The side wall which is cut out now to allow access to drink was roughly 2.5 inches thick, and the tread area of the tire is a solid 6 inches thick. And while our winter is very mild this year it has not even tried to freeze even when the regular tanks have froze 4-6 inches thick. I put a 3/4 inch automatic float valve in the center of the tire coming up from where the rim would go in the inside. This makes it stay full and fresh all the time. So free tire plus concrete (about 8 bags) and the valve made my tank roughly $120. And I don't have to worry about the horses big clod feet slapping the tank when they drink and making it leak. I did forget to mention I did bury the tire to where only about 6-8 inches of it is above ground to help protect against the colder winters we usually have but that's not necessary I'm told. I have the second started now and when my hole dries out a bit from the rain we just had, i'll finish it up and backfill it as well. I'll try and get some pictures of it and add to the post later.