1. First, ask about the septic system. The best way to find out what you want to know about the septic system is to ask. You can ask whatever questions you would like to, but it is vitally important to ask, where is it, what's installed, and most important what the service and repair history are. If there has been a long list of repairs done, then you should probably speak with the contractors that did the repairs to get their expert opinion on the state of the septic system and whether or not it is worth your trouble.

2. Next, you want to be sure to make a visual inspectionfor signs of trouble: Look for wet areas, smelly areas, rocky areas, areas of recent excavation. Also make note of the location of and distance to nearby streams, private wells, ponds, buildings, property lines, and rocky areas, and areas of trees and shrubbery. Warning: be very alert for evidence of sink holes or subsidence. Do not walk over anything suspicious as you might step into or fall into a collapsing system.

Once you know the locations of the septic tank and leaching fields you should take the time to walk over the entire area and observe whether there is any evidence of a sewage overflow condition. Greener grass in the leaching area may not necessarily indicate a system problem. If, however the area is completely saturated and odorous you should be very concerned. It most likely indicates an active failure. So, use your eyes and look for anything that might indicate expense later on. If you aren't sure on something it is safer to have an expert come out and check then to pay the price later.

3. Perform a septic loading and dye test to see if it produces evidence of a failure. This is a good idea no matter what the said conditions and visual conditions of the septic system are. Most home inspections do not include checking the septic system. This is an extra, but be sure to hire a home inspector who knows how to perform and will include this test.

4. Pump the tank and inspect for additional clues, depending on what you learned at 1,2,3. This is really necessary if you had negative results with the first three steps.

5. Take the time to do any additional septic system physical investigations that might be needed.
If you use these steps you will likely not get yourself into trouble with the home you buy having a faulty septic tank or system. You can avoid costly repairs by taking these precautions.