Discovered today that the line from the tank to the drain field had 'solids' in it. That's not good. I'd heard that nothing but clear water was to drain out of the tank. I used a pump to remove enough water from the line that it's all clear now. Looks like I'm going to have to remove the tank lid to be sure the outlet T is still in place. About 7 years ago, I replaced the line from the tank to the drain field. No problems then with the field draining properly. I tested it with a garden hose running full open at 80psi for a solid 10min into the drain line. Never backed up at all. So something between then and now has changed. I'm the only one here and the system is designed for a family of four. I may try a strong acid or alkaline followed by water or air pressure to force it down and out the holes in the laterals. Any suggestions?