What size septic tank do I need? # Bedrooms Home Square Footage Tank Capacity 1 or 2 Less than 1,500 750 3 Less than 2,500 1,000 4 Less than 3,500 1,250 5 Less than 4,500 1,250 Click to see full answer. Similarly, how often do you need to pump a 1000 gallon septic tank?For example, a 1,000 gallon septic tank, which is used by two people, should be pumped every 5.9 years. If there are eight people using a 1,000-gallon septic tank, it should be pumped every year.Likewise, can a septic tank be too big? If the tank is too small for your water usage, the wastewater gets forced out prematurely before everything settles because more water is coming. It would make sense to assume bigger is better, but a tank that’s too big for your water consumption can mess with the bacteria forming. Similarly, you may ask, how big of a septic field do I need? A typical septic drainfield trench is 18 to 30 inches in depth, with a maximum soil cover over the disposal field of 36″; or per the USDA, 2 feet to 5 feet in depth. At REFERENCES we cite these sources.What are the dimensions of a 1000 gallon septic tank? 1000 GALLON SEPTIC TANK LENGTH 102″, WIDTH 69″, HEIGHT 59″, WEIGHT 8600 LBS.