[Egnalf]

Average human ( not flex) produces about 325 pounds of pooh per year. One gallon of pooh is roughly 8 pounds depending upon moisture content. Some of that goes away as moisture. So, assume 275 pounds per human per year if your stool is really, really dense. Fill it halfway, or 625 gallons, that is 5000 pounds. How many humans in that house to fill it that much in three years?

3years x 275=825. Even if you have six, hard pooping mofos, that tank isn't full.