Reference
Concrete tank dimensions vary a little by manufacturer, but the standard sizes cluster tightly. These are typical single-compartment concrete figures — plastic and fibreglass tanks run similar footprints at a fraction of the weight.
| Capacity | Footprint (W x L) | Height | Weight (concrete) | Typical use |
|---|---|---|---|---|
| 750 gal | 4' x 8' | 5' – 5'6" | approx. 8,000 lb | 1–2 bedroom homes, small cabins |
| 1000 gal | 5' x 8'6" | 5' – 6' | approx. 10,500 lb | the standard 3-bedroom tank in most states |
| 1250 gal | 5'6" x 9' | 5'6" – 6' | approx. 12,000 lb | 4-bedroom homes |
| 1500 gal | 6' x 10' | 5'6" – 6'6" | approx. 14,000 lb | 5-bedroom homes; the Massachusetts minimum |
| 2000 gal | 6' x 12' | 6' – 7' | approx. 17,500 lb | large homes, small commercial |
The workhorse. Roughly 5 feet wide, 8 and a half feet long, and about 5 feet tall, weighing around five tons in concrete. It is the legal minimum for a three-bedroom home in most states, which makes it the most manufactured and usually the cheapest per gallon.
About 6 by 10 feet and up to 6 and a half feet tall. It is the minimum for five-bedroom homes in most states — and the minimum for every home in Massachusetts under Title 5. If you are between sizes, the incremental cost of stepping up to 1,500 is small against the drainfield it protects.
Typically the lid sits 4 inches to 4 feet below grade. Deeper burial needs risers to bring access to the surface — worth specifying on any new install, because every future pump-out otherwise starts with a shovel.
Capacity is set by bedrooms and your state's minimum, not by the tank that happens to fit the hole. Run the tank size calculator for your state's figure, and see the size chart for the full bedroom table.
The excavation runs about 2 feet larger than the tank on every side, and the delivery truck needs to park within boom reach — usually 15 feet of the hole for a standard boom truck. Tight urban lots sometimes dictate two smaller tanks in series, or a plastic tank that can be carried in.