Septic tank size by state / New England
Connecticut septic tank size
In Connecticut the minimum septic tank for a three-bedroom house is 1,000 gallons, rising to 1,125 gallons at four bedrooms. The figure comes from Public Health Code §19-13-B103. That matches the 1,000-gallon median of the 47 states listed here.
What the Connecticut rule says
The rule is Public Health Code §19-13-B103; Technical Standards for Subsurface Sewage Disposal Systems (Sept. 2026 edition, eff. Sept. 1, 2026), §8.2.1 Table 5; §8.2.4; design flow §7.1, administered by Connecticut Department of Public Health (DPH). In its own words:
Table 5. Septic Tank Sizing for Residential Buildings ... Single-Family ... 1-3 Bedrooms 1,000 Gallons ... Each Bedroom Above 3 Add 125 Gallons per Bedroom
Source: Public Health Code §19-13-B103, read 2026-10-20.
- The 2026 Technical Standards add 125 gallons for each bedroom above three in a single-family home.
- A garbage grinder adds 250 gallons; bedrooms in an outbuilding add 225 gallons each.
Connecticut minimum tank size by bedrooms
| Bedrooms | Minimum tank | Versus the median state |
|---|---|---|
| 1 | 1,000 gal | same |
| 2 | 1,000 gal | — |
| 3 | 1,000 gal | same |
| 4 | 1,125 gal | −75 |
| 5 | 1,250 gal | −250 |
| 6 | 1,375 gal | — |
The first step up comes at 4 bedrooms, from 1,000 to 1,125 gallons, and a six-bedroom house needs 1,375 gallons. Beyond the table the rule adds 125 gallons for each extra bedroom. These are minimums: the permit can call for more, and a bigger tank needs pumping less often.
How Connecticut compares with nearby states
Maine requires 1,000 gallons for three bedrooms; Massachusetts requires 1,500 gallons for three bedrooms; New Hampshire requires 1,250 gallons for three bedrooms; Rhode Island requires 1,000 gallons for three bedrooms; Vermont requires 1,000 gallons for three bedrooms. 37 of the 47 states listed here share Connecticut's three-bedroom figure.
Before you size a tank in Connecticut
- Bedrooms, not people, set the size in most rules. Rooms that could be used as bedrooms are usually counted, so check how your permitting office counts a den or a finished basement.
- Garbage disposals, grinder or ejector pumps and large tubs change the answer in many states; the points above list Connecticut's adjustments.
- The tank is only half the system. The drainfield is sized separately from soil tests, and it is usually the bigger cost.
- A private well on the same lot has its own setbacks from the tank and field; the well pump and pressure tank calculators size the water side.
Figures are the state's minimum as written on 2026-10-20. Local health departments can require more; the permit issued for your property governs. See the methodology for how each state was read.