Septic tank sizes by bedrooms
The minimum septic tank size for a single-family home is set by state rule — usually by bedroom count, sometimes by daily design flow. Here are the actual figures from eight state codes, with the rule citations, and what each does about a garbage disposal.
These are state minimums. Counties and local health districts can and do require more; your installer or the health department issuing the permit has the final word.
State minimums compared
| State / rule | 2 BR | 3 BR | 4 BR | 5 BR | Garbage disposal |
|---|---|---|---|---|---|
| Minnesota Minn. R. 7080.1930 | 1,000 | 1,000 | 1,500 | 1,500 | +50 % |
| New York 10 NYCRR App. 75-A.6 | 1,000 | 1,000 | 1,250 | 1,500 | Counts as one more bedroom |
| North Carolina 15A NCAC 18E .0801 | 1,000 | 1,000 | 1,000 | 1,250 | Doubled only if a grinder or lift pump feeds the tank |
| Ohio OAC 3701-29-12(C) | 1,000 | 1,500 | 2,000 | 2,000 | No adjustment |
| Pennsylvania 25 Pa. Code § 73.31 | 900* | 900* | 1,250* | 1,400* | Already in the design flow |
| Texas — standard fixtures 30 TAC § 285.91 | 750* | 1,000* | 1,250* | 1,250* | No adjustment |
| Texas — water-saving fixtures 30 TAC § 285.91 | 750* | 750* | 1,000* | 1,250* | No adjustment |
| Florida F.A.C. 62-6.008 | 900* | 900* | 1,050* | 1,200* | No adjustment |
| Washington WAC 246-272A-0232 | 1,000 | 1,000 | 1,000 | 1,250 | No adjustment |
* Computed from the rule's daily-flow formula; these states size the tank from design flow rather than printing a bedroom table. Florida assumes the home's floor area falls inside the band for its bedroom count — a larger house is sized on area.
The rules, state by state
Minnesota — Minn. R. 7080.1930, Table V
| Bedrooms | Minimum |
|---|---|
| 3 or fewer | 1,000 gal |
| 4–5 | 1,500 gal |
| 6–7 | 2,000 gal |
| 8–9 | 2,500 gal |
| Over 9 | 2,500 + 250 per bedroom over 9 |
A garbage disposal, or a sewage ejector or grinder pump, raises the requirement by 50 % and calls for multiple compartments or tanks; the two increases are not added together.
New York — 10 NYCRR Part 75, Appendix 75-A.6(a), Table 3
| Bedrooms | Minimum | Min. liquid surface area |
|---|---|---|
| 1–3 | 1,000 gal | 27 ft² |
| 4 | 1,250 gal | 34 ft² |
| 5 | 1,500 gal | 40 ft² |
| 6 | 1,750 gal | 47 ft² |
| Each over 6 | +250 gal | +7 ft² |
“A garbage grinder shall be considered equivalent to an additional bedroom for determining tank size.” An expansion attic counts as a bedroom too.
North Carolina — 15A NCAC 18E .0801, Table XIV
| Bedrooms | Minimum |
|---|---|
| 4 or fewer | 1,000 gal |
| 5 | 1,250 gal |
| More than 5 | By daily flow Q (Table XV): 2Q up to 600 gpd; 1.17Q + 500 above |
The 18E rules replaced the old 18A .1900 rules from 1 January 2024 (amended 1 June 2026). “The minimum capacity of any septic tank shall be 1,000 gallons.” Tanks must have two compartments (or two tanks in series) and an effluent filter, and the capacity is doubled where a grinder or lift pump discharges to the tank.
Ohio — OAC 3701-29-12(C)(1)
| Bedrooms | Minimum |
|---|---|
| 1–2 | 1,000 gal |
| 3 | 1,500 gal in two tanks or compartments |
| 4–5 | 2,000 gal |
| 6 or more | 2,500 gal + 250 gal per bedroom (see note) |
For six or more bedrooms the rule reads “2,500 gallons plus 250 gallons for each bedroom”; read literally that is every bedroom, though it is likely intended as each bedroom over six. Ask the local health district which reading it applies.
Pennsylvania — 25 Pa. Code § 73.31
Pennsylvania sizes from design flow: 400 gallons per day for up to three bedrooms plus 100 gpd for each additional bedroom. Up to 500 gpd the tank is 3.5 × (flow − 400) + 900 gallons; from 500 to 5,000 gpd it is 1.5 × (flow − 500) + 1,250. That gives 900 gal for 1–3 bedrooms, 1,250 for 4, 1,400 for 5 and 1,550 for 6. “The minimum liquid septic tank capacity for any installation is 900 gallons,” and the design flow already allows for a garbage grinder.
Texas — 30 TAC § 285.91, Tables II and III
| Design flow Q | Minimum tank |
|---|---|
| Up to 250 gpd | 750 gal |
| 251–350 gpd | 1,000 gal |
| 351–500 gpd | 1,250 gal |
| 501–1,000 gpd | 2.5 × Q |
| Bedrooms (floor area up to) | Standard fixtures | Tank | Water-saving fixtures | Tank |
|---|---|---|---|---|
| 1–2 (1,500 ft²) | 225 gpd | 750 | 180 gpd | 750 |
| 3 (2,500 ft²) | 300 gpd | 1,000 | 240 gpd | 750 |
| 4 (3,500 ft²) | 375 gpd | 1,250 | 300 gpd | 1,000 |
| 5 (4,500 ft²) | 450 gpd | 1,250 | 360 gpd | 1,250 |
| 6 (5,500 ft²) | 525 gpd | 1,313 | 420 gpd | 1,250 |
A minimum liquid depth of 30 inches applies. TCEQ has an open rulemaking that may revise the sizing tables; check its rules page for adoption.
Florida — F.A.C. 62-6.008 (formerly 64E-6.008), Tables I and II
| Bedrooms (floor area) | Design flow | Minimum tank |
|---|---|---|
| 1 (up to 750 ft²) | 100 gpd | 900 gal |
| 2 (751–1,200 ft²) | 200 gpd | 900 gal |
| 3 (1,201–2,250 ft²) | 300 gpd | 900 gal |
| 4 (2,251–3,300 ft²) | 400 gpd | 1,050 gal |
| Each extra bedroom or 750 ft² | +60 gpd | Table II: 401–500 gpd → 1,200; 501–600 → 1,350 |
The larger of the bedroom count or the floor area sets the flow. Tanks must be multi-chamber (or tanks in series) with an outlet filter. The rule is now administered by the Department of Environmental Protection.
Washington — WAC 246-272A-0232, Table VII
| Bedrooms | Minimum |
|---|---|
| 4 or fewer | 1,000 gal |
| Each additional | +250 gal (5 = 1,250; 6 = 1,500) |
Current rules took effect 1 April 2025. Tanks need two compartments, the first holding one-half to two-thirds of the volume.
Michigan
Michigan has no statewide residential septic code; each local health department sets its own sanitary code. Ask your county health department for its tank table.
The federal reference point
There is no federal minimum. The US EPA's Onsite Wastewater Treatment Systems Manual (EPA/625/R-00/008) reproduces a model table and notes that “in many jurisdictions the minimum tank volume has been increased to 1,000 gallons or more.”
| Bedrooms | 1 | 2 | 3 | 4 | 5 | 6 | 7 | 8 |
|---|---|---|---|---|---|---|---|---|
| Gallons | 750* | 750* | 1,000 | 1,200 | 1,425 | 1,650 | 1,875 | 2,100 |
* “Many states have established 1,000 gallons or more as the minimum size.”
What a septic tank looks like at each size
Dimensions are set by each manufacturer, not by code. These are examples from manufacturers' own product listings, to give a sense of scale and weight — not a standard.
| Capacity | Manufacturer / product | Dimensions | Weight |
|---|---|---|---|
| 1,000 gal | Oldcastle Infrastructure — Septic Tank 1000 Gal., non-traffic | 8 ft L × 4 ft 4 in W × 5 ft H | 9,130 lb |
| 1,250 gal | Jensen Precast — 1250 gal pedestrian-rated (Arizona market) | 125 × 61 × 72 in outside | 15,004 lb |
| 1,500 gal | Oldcastle Infrastructure — 5×10 Septic Tank 1500 Gal. (CST-1500) | 10 ft × 5 ft × 5 ft H | 21,600 lb |
For a tank you can measure, inside length × width × liquid depth ÷ 231 gives US gallons — or use the rectangular tank volume calculator. Indian homes are sized under IS 2470 instead; see the septic tank size calculator (litres).
FAQ
What size septic tank do I need for a 3-bedroom house?
1,000 gallons in most states with a bedroom table (Minnesota, New York, North Carolina, Washington). Ohio requires 1,500 gallons for three bedrooms; Pennsylvania and Florida allow 900; Texas allows 750 with water-saving fixtures. Your county can require more than the state minimum.
What size septic tank for a 4-bedroom house?
From 1,000 gallons (North Carolina, Washington, Texas with water-saving fixtures) to 2,000 gallons (Ohio). 1,250 is the commonest figure — New York, Pennsylvania and Texas with standard fixtures — and Minnesota requires 1,500.
Does a garbage disposal mean a bigger septic tank?
In some states. Minnesota adds 50 %; New York counts a garbage grinder as an extra bedroom. Texas, Florida, Washington and Ohio make no adjustment, and Pennsylvania's design flow already allows for one.
What are the dimensions of a 1,000 gallon septic tank?
It depends on the maker. One example: Oldcastle Infrastructure lists a 1,000-gallon non-traffic precast tank at 8 ft long, 4 ft 4 in wide and 5 ft high, weighing 9,130 lb. Plastic and fiberglass tanks are shaped very differently.
How do I find out how big my existing septic tank is?
Check the permit or as-built drawing held by your county health department — most record the tank size. Otherwise measure the inside length, width and liquid depth when it is pumped and enter them in the rectangular tank volume calculator.
Sources and standards
- Minn. R. 7080.1930 — Septic tank capacity (Table V)Minnesota Office of the Revisor of Statuteshttps://www.revisor.mn.gov/rules/7080.1930/
- 10 NYCRR Part 75, Appendix 75-A.6(a), Table 3 (effective 16 March 2016)New York State Department of Healthhttps://www.health.ny.gov/regulations/nycrr/title_10/part_75/appendix_75-a.htmNYSDOH's compiled PDF is marked unofficial; the table also appears on the official regulations site.
- 15A NCAC 18E .0801 — Septic tank capacity (eff. 1 Jan 2024; amended 1 Jun 2026)North Carolina Office of Administrative Hearingshttp://reports.oah.state.nc.us/ncac/title%2015a%20-%20environmental%20quality/chapter%2018%20-%20environmental%20health/subchapter%20e/15a%20ncac%2018e%20.0801.pdf
- OAC 3701-29-12 — Tanks, pumps and controls, and building sewers (eff. 1 Jan 2015)Ohio Laws and Administrative Ruleshttps://codes.ohio.gov/ohio-administrative-code/rule-3701-29-12
- 25 Pa. Code § 73.31 — Standards for septic tanksPennsylvania Code & Bulletinhttps://www.pacodeandbulletin.gov/Display/pacode?file=/secure/pacode/data/025/chapter73/s73.31.html
- 30 TAC § 285.91 — Tables (as adopted; § 285.91 last amended eff. 6 July 2023)Texas Commission on Environmental Qualityhttps://www.tceq.texas.gov/downloads/rules/adoptions/21030285_ado.pdf
- F.A.C. 62-6.008 — System Size Determinations (formerly 64E-6.008; eff. 16 July 2013)Florida Administrative Codehttps://www.flrules.org/gateway/ruleNo.asp?id=62-6.008
- WAC 246-272A-0232 — Septic tank design (WSR 24-06-046, eff. 1 April 2025)Washington State Legislaturehttps://app.leg.wa.gov/wac/default.aspx?cite=246-272A-0232
- Senate Fiscal Agency analysis of SB 299–300 (2023–2024)Michigan Legislaturehttps://archive.legislature.mi.gov/documents/2023-2024/billanalysis/Senate/htm/2023-SFA-0299-F.htm“Michigan is the only state without uniform standards for onsite wastewater treatment systems.”
- Onsite Wastewater Treatment Systems Manual (EPA/625/R-00/008), p. 4-40, Table 4-13U.S. Environmental Protection Agencyhttps://www.epa.gov/sites/default/files/2015-06/documents/2004_07_07_septics_septic_2002_osdm_all.pdf
- Septic Tank — 1000 Gal. — Non-Traffic RatedOldcastle Infrastructure (manufacturer)https://oldcastleinfrastructure.com/product/septic-tank-1000-gal-non-traffic-rated-2
- Pedestrian Rated Septic Tank — 1250 gal — AZ MarketJensen Precast (manufacturer)https://jensenprecast.com/products/septic-tank-pjs-1250-gal-24e-24e-pedestrian-rated
- 5′×10′ Septic Tank 1500 Gal.Oldcastle Infrastructure (manufacturer)https://oldcastleinfrastructure.com/product/5x10-septic-tank-1500-gal
Every linked source above was retrieved and checked on 2026-11-01.