Here in Texas, it's very common to do your own septic system. When I spoke to the Country Health Inspector, he told me that I had to have ten acres of land, or more, and that I was responsible for all repairs to it.
Home Depot sells septic tanks here. They have them sitting out in their parking lot, and if you want one, you need to buy it right away, because they sell them pretty quickly. When I bought mine,
Norwesco 1000 Gal. 2 MH 2 CPT Septic Tank 44474 - The Home Depot, they had just received a new deliver of three big 1,000 gallon tanks, and three 500 gallon tanks. I went there the next week and they where all sold out!!!! But they always get more.
Installing the tank is pretty easy. I did it by myself. Just dig the hole big enough to be able to get in there and level it off really good at the depth you want it. I think the shovel work at getting it super flat was the hardest part. The tank isn't very heavy, I hooked it to my backhoe with a chain and lowered it into the hole.
To get to my leach field, I used Schedule 40 PVC. Same thing I used going from my house to the tank. Thin wall PVC is also used by some people, but Schedule 40 is so much stronger that I feel it's worth the extra money.
MY leach field is shaped kind of like the letter E. The line from the tank goes to the middle of the E, then it splits and heads out to three separate lines that are about ten feet apart. Home Depot and Lowes both sell all the stuff you need to make your own leach field.
NDS 4 in. x 10 ft. EZ-Drain Prefabricated French Drain with Pipe EZ-0802F - The Home Depot
On my house, I have all my drain lines going into my tank, but I've worked on a bunch of houses here that have a Grey line going out into their landscaping. Showers and bathtub water probably shouldn't go into a septic tank, it dilutes the solids too much and slows down the process of breaking them down, but I didn't understand that when I built my house. If I could go back in time, I would have a separate Grey line