The most expensive mistake in septic work is replacing a drain field that wasn't the problem. A cracked outlet baffle can flush scum into the lines for years, and the field gets blamed. A tilted distribution box can drown one trench while three others sit dry, and the whole field gets condemned. So we work from the house outward and prove each part before we move on to the next.
First we find the tank and open it. As a Georgia DPH-approved pumper we can pump it on the same visit, and pumping is also a test. Before the hose goes in, we note where the liquid sits against the outlet. When we pump the tank down, we watch whether effluent runs backward out of the outlet pipe. Backflow from the outlet means the water has nowhere to go downstream. A normal level with the house still backing up puts the problem on the inlet side.
With the tank empty we can see the baffles. Concrete baffles crack and fall off. Older sanitary tees can snap at the joint, clog, or be missing entirely. The DPH additives advisory warns that acids in some additives "can actually corrode concrete septic tanks and distribution boxes" (Georgia DPH). If the outlet baffle has been gone a long time, we tell you plainly that the field has probably taken solids, and we check it next rather than assuming.
Next is the distribution box. We dig it up and run water through it. Every outlet should take an even share. If one outlet sits lower, or roots or solids are choking another, the box gets leveled, cleaned or replaced, and flow-equalizer caps can be set on the outlets. On pumped systems we check the pump, floats, panel and screen in the pump tank. That includes whether the float tree is tangled in the cord and whether the pump is actually moving water.
Only after the tank, pipes, D-box and pump are cleared do we call a drain field failed. If it is the field, you don't have to start over with a second company. The same crew that found the problem digs the lines too, under the same permit conversation with Environmental Health. The field side has its own page: drain field repair and replacement.