A 1,000 gallon septic tank is the default residential size in the United States. It is the smallest tank almost any county will permit on a new house, and it is the right tank for most one, two and three bedroom homes. Search results treat 500, 1,000 and 1,500 gallons as three different products. They are three rows on the same manufacturer list, and the row you need is set by bedroom count and a 48-hour retention rule, not by preference.
Stock tank sizes you can actually buy
Precast plants pour a short list. Anything in between is rounded up, because nobody custom-casts an 1,100 gallon tank for a house. The list the calculators on this site snap to is 500, 750, 1,000, 1,250, 1,500, 1,750, 2,000, 2,500 and 3,000 gallons.
| Bedrooms | Minimum tank | Why |
|---|---|---|
| 1 to 3 | 1,000 gal | Code floor. A 500 or 750 is not permitted new. |
| 4 | 1,250 gal | Bedroom table steps up 250 gal. |
| 5 | 1,500 gal | Bedroom table. |
| 6 | 1,750 gal | Bedroom table. |
| Each extra bedroom | +250 gal | Then snap up to the next stock size. |
Two other rules can beat the bedroom table. The tank must hold at least two days of design flow (120 gallons per bedroom per day on the common baseline, or 60 gallons per occupant if the house is more crowded than the bedroom count implies), and almost no jurisdiction permits a new tank under 1,000 gallons. The septic tank size calculator runs all three and tells you which one governed.
1,000 gallon septic tank dimensions
There is no single drawing. Each precast plant has its own form, and a 1,000 gallon tank from two plants twenty miles apart will not drop into the same hole. What is typical for a concrete residential tank:
| Size | Typical L x W x H | Typical weight |
|---|---|---|
| 500 gal | 5 to 8 ft x 4 to 5.5 ft x 4 to 5 ft | 4,400 to 6,000 lb |
| 1,000 gal | 8 to 8.5 ft x 5 to 5.7 ft x 5 to 5.3 ft | 8,000 to 8,600 lb |
| 1,500 gal | 10 to 12 ft x 5.5 to 6 ft x 5 to 5.7 ft | 10,750 to 12,500 lb |
| 2,000 gal | 11.5 to 13 ft x 6 to 6.5 ft x 5.5 to 6 ft | 14,000 to 16,000 lb |
A 1,000 gallon concrete tank is roughly eight feet long, five and a half feet wide and five feet tall, and it weighs four tons. That is why a crane or a large excavator sets it, and why the access path to the yard matters as much as the hole. Plastic and fiberglass tanks of the same volume are a few inches different and a fraction of the weight, which is their whole selling point on a tight lot.
1,000 gallon concrete septic tank
Concrete is the default for a reason. A well-made tank lasts 40 years and more, sits still in a high water table and does not float when pumped empty. The risks are a cracked seam if it was set on an uneven bed, and corrosion of the concrete above the waterline in some soils. Two lids are typical, one over the inlet and one over the outlet, which is what you want for a real pump-out.
500 gallon septic tank
A 500 gallon tank is a real product and a common search, and it is almost never a legal primary tank for a house. New codes put the floor at 1,000 gallons. What a 500 is used for: a pump chamber downstream of the real tank, a holding tank on a seasonal cabin, or extra volume added to an old undersized system. If a listing says the house has a 500 gallon septic tank, budget to replace it. The tank you have is a pump-out every year or two for a family of three (1.5 years on the Penn State table) and a red flag at sale.
1,500 gallon septic tank
A 1,500 gallon tank is the bedroom-table size for a five bedroom house, and the next stock size people actually mean after 1,000. It costs more to buy and more to pump per visit, and less to own, because the same household goes longer between pump-outs. Dimensions, the pumping-interval comparison and when a smaller house should step up live on the 1,500 gallon septic tank page.
The full bedroom table, every stock size plants pour and typical concrete dimensions are on the septic tank size chart. This page stays on the 1,000 gallon tank, because that is the one most houses actually get.
What a tank costs
The tank itself, supplied and set, runs about $1,200 to $3,600 for a 1,000 gallon concrete unit on the national range this site uses, and more as capacity goes up. That is one line on a $6,000 to $15,000 conventional system. Plastic is often cheaper to buy and more expensive to ballast in a wet hole. Steel is the one to refuse: it rusts from the inside in 20 to 30 years and the lid can fail without warning.