Data source
The files behind the cost figures, the check against the Census Bureau's own table, and the state regulations behind the tank sizes.
The survey and the files
- Survey: American Housing Survey (AHS), sponsored by the U.S. Department of Housing and Urban Development and conducted by the U.S. Census Bureau.
- Files: the national public use files of the 2019, 2021 and 2023 surveys.
- Where to get them: the Census Bureau's AHS file directory, www2.census.gov/programs-surveys/ahs/, one folder per survey year.
- What we read: the job records (kind of job, cost, who did the work, year, main source of money) and, for each home, its weight, region, size, bedrooms, year built, sewage disposal and water supply, together with the flags that mark values the Census Bureau changed.
| File | Job records | Septic tank jobs |
|---|---|---|
| AHS 2019 National PUF v1.1 | 47,125 | 166 |
| AHS 2021 National PUF v1.0 | 51,476 | 156 |
| AHS 2023 National PUF v1.1 | 44,689 | 149 |
Source: U.S. Census Bureau and U.S. Department of Housing and Urban Development, American Housing Survey, national public use files. The calculations are our own. The Census Bureau has not reviewed or endorsed this site or its figures.
The price index
- Series: price index for residential improvements, that is, home improvements (National Income and Product Accounts, Table 5.4.4, line 46; series B946RG), U.S. Bureau of Economic Analysis (BEA).
- Where to get it: the BEA publishes all series of its national accounts in one text file, apps.bea.gov/national/Release/TXT/NipaDataQ.txt. The figures here use the file released September 30, 2026; its latest quarter is the second quarter of 2026.
- What we do with it: a cost reported for a job done in a given year is multiplied by the latest value of the index divided by that year's average. The methodology page lists the factors.
Source: U.S. Bureau of Economic Analysis, National Income and Product Accounts. The BEA has not reviewed or endorsed this site or its figures.
Check against the Census Bureau's own table
The Census Bureau publishes a workbook, "Table Specifications and PUF Estimates for User Verification", for users to test their calculations; its table C-16-OO covers home improvement costs. Each time our data is built, the number of jobs, the median and the mean of every row are recalculated from the 2023 national file, with every record included as the Bureau does. 35 of 35 rows match.
| Survey category | Jobs, ours | Jobs, Census | Median, ours | Median, Census | Mean, ours | Mean, Census |
|---|---|---|---|---|---|---|
| All jobs | 139,946 | 139,946 | $2,000 | $2,000 | $6,170 | $6,170 |
| Septic tank | 548 | 548 | $5,000 | $5,000 | $7,924 | $7,924 |
The figures on the cost page differ from this table on purpose: they leave out the costs the Census Bureau filled in, cover homes on a septic system only, separate professional from do-it-yourself jobs, read three surveys together and are in 2026 prices.
Homes on a septic system in the 2023 survey
| Sewage disposal | Share | Surveyed |
|---|---|---|
| Public sewer | 81.4% | 41,635 |
| Standard septic tank and leach field | 17.6% | 6,253 |
| Septic system that uses a pump to distribute wastewater | 0.6% | 237 |
| Septic system elevated above the natural soil surface | 0.3% | 91 |
| Septic system that applies treated wastewater | 0.1% | 20 |
| Other type of septic system | 0.1% | 33 |
All septic systems together: 18.6% of occupied homes (6,634 surveyed). 10.4% of occupied homes get their water from a private well.
Places the files identify
The national file gives each home's Census division, from which we take its region. The files do not identify states.
| Region | States |
|---|---|
| Northeast | Connecticut, Maine, Massachusetts, New Hampshire, New Jersey, New York, Pennsylvania, Rhode Island, Vermont |
| Midwest | Illinois, Indiana, Iowa, Kansas, Michigan, Minnesota, Missouri, Nebraska, North Dakota, Ohio, South Dakota, Wisconsin |
| South | Alabama, Arkansas, Delaware, District of Columbia, Florida, Georgia, Kentucky, Louisiana, Maryland, Mississippi, North Carolina, Oklahoma, South Carolina, Tennessee, Texas, Virginia, West Virginia |
| West | Alaska, Arizona, California, Colorado, Hawaii, Idaho, Montana, Nevada, New Mexico, Oregon, Utah, Washington, Wyoming |
The state regulations behind the tank sizes
- Source: the regulation each state publishes itself, or the state's own standards where it sets the size there. No other website is used.
- What they give: 39 set the smallest tank in a table by bedrooms, 8 set it from a daily flow per bedroom, and 4 give no size by bedrooms.
- When: read on October 8, 2026.
- Copies: 25 of the 51 were read in the copy the Internet Archive keeps of the state's own address, because the state's site could not be reached. The table says which.
| State | Rule | Wording | Read in |
|---|---|---|---|
| Alabama | Ala. Admin. Code r. 420-3-1-.17(5), Table 9Alabama Department of Public Health | Tank Sizing. The effective liquid capacity of a septic tank for a dwelling shall be based on the number of bedrooms proposed and shall, at a minimum, comply with Table 9. Table 9, Septic Tank Capacities for Dwellings Without Advanced Treatment. Number of Bedrooms, Minimum Effective Liquid Capacity (gal): 4 or fewer, 1,000; 5, 1,500; Each additional bedroom, add 250. | The state's site |
| Alaska | 18 AAC 72.530(e)(2), table Minimum Septic Tank SizeAlaska Department of Environmental Conservation | The net minimum volume of a septic tank must be in accordance with requirements set out in the following table. Minimum Septic Tank Size. Residential Dwellings, Number of Bedrooms, Minimum Tank Size: 0 - 3, 1,000 gallons; 4 - 8, 1,000 plus 250 gallons for each bedroom over three; 9 - 13, 2,500 gallons; 14 - 18, 3,000 gallons. | Internet Archive copy of 2025-01-19 |
| Arizona | A.A.C. R18-9-A314(4)(a)(i), table Criteria for Septic Tank Size and Design FlowArizona Department of Environmental Quality | The design liquid capacity of the septic tank and the septic tank's daily design flow are determined based on the number of bedrooms and fixture count as follows: Criteria for Septic Tank Size and Design Flow. Number of Bedrooms, Fixture Count, Minimum Design Liquid Capacity (gallons): 1, 7 or less, 1000; More than 7, 1000; 2, 14 or less, 1000; More than 14, 1000; 3, 21 or less, 1000; More than 21, 1250; 4, 28 or less, 1250; More than 28, 1500; 5, 35 or less, 1500; More than 35, 2000; 6, 42 or less, 2000; More than 42, 2500. | Internet Archive copy of 2025-10-11 (Supp. 25-2) |
| Arkansas | Arkansas State Board of Health, Rules Pertaining to Onsite Wastewater Systems (2024), Appendix CArkansas Department of Health | Appendix C. Minimum Capacity of Septic Tanks. Liquid Capacity of Tank (Gallons). Number of Bedrooms, Residential: 1, 2, and 3, 1000. Note: For each additional bedroom add 250 gallons. | The state's site |
| California | State Water Resources Control Board, Water Quality Control Policy for Siting, Design, Operation, and Maintenance of Onsite Wastewater Treatment Systems (OWTS Policy), section 8.2California State Water Resources Control Board | New and replacement OWTS septic tanks shall be limited to those approved by the International Association of Plumbing and Mechanical Officials (IAPMO) or stamped and certified by a California registered civil engineer as meeting the industry standards, and their installation shall be according to the manufacturer's instructions. | Internet Archive copy of 2026-03-24 |
| Colorado | 5 CCR 1002-43 (Regulation No. 43), section 43.9(B)(2)(a), Table 9-1Colorado Department of Public Health and Environment, Water Quality Control Commission | Sizing for residential capacity for new installations must be based upon the number of bedrooms according to Table 9-1: Minimum Septic Tank Size Based on Number of Bedrooms. Number of Bedrooms, Tank Capacity (gallons): 2 or 3, 1,000; 4, 1,250; Each Additional, 250. | The state's site |
| Connecticut | Technical Standards for Subsurface Sewage Disposal Systems (effective September 1, 2026), section 8.2.1, Table 5, under Connecticut Public Health Code §§ 19-13-B103a to 19-13-B103gConnecticut Department of Public Health | The required capacity (volume) of a septic tank serving a residential building shall be based on Table 5. 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. Whenever more than 25% of the building's design flow is pumped into the septic tank, the size of the tank shall be increased 50% beyond the minimum capacity required per sections 8.2.1 and 8.2.2. Garbage Grinder, Add 250; Large Bathtub (100-200 gallons), Add 250; Large Bathtub (Over 200 gallons), Add 500. | Internet Archive copy of 2026-10-08 |
| Delaware | 7 Del. Admin. Code 7101, § 5.3.14.4, with the design flow of § 5.3.3.3Delaware Department of Natural Resources and Environmental Control | The minimum liquid working capacity of septic tanks shall be: For flows ≤ 500 gpd the minimum liquid working capacity shall be 1,000 gallons. For flows > 500 gpd but < 2,500 gpd shall have a working capacity of 1.5 times the expected flow rate with a minimum liquid working capacity of 1,500 gallons. The design wastewater flow from residential dwellings, including single family, multiple family, manufactured homes, and apartments served by on site wastewater treatment and disposal systems shall be 120 gallons per day per bedroom. | The state's site |
| District of Columbia | District of Columbia Plumbing Code (2017): 2015 International Plumbing Code as amended by 12-F DCMRDistrict of Columbia Department of Buildings. 12-F, Plumbing Code Supplement of 2017: § 101 and chapter 7, Sanitary Drainage | The District of Columbia Plumbing Code (2017), referred to as the Plumbing Code, consists of the 2015 edition of the International Plumbing Code (International Plumbing Code), published by the International Code Council (ICC), as amended by the Plumbing Code Supplement of 2017 (12-F DCMR). The International Plumbing Code is copyrighted by the ICC and therefore is not republished here. | The state's site |
| Florida | Florida Administrative Code, Rule 62-6.008, Tables I and IIFlorida Department of Environmental Protection | Minimum effective septic tank capacity and total dosing tank capacity shall be determined from Table II. Table II, Septic Tank and Pump Tank Capacity. Average sewage flow, gallons/day; septic tank minimum effective capacity, gallons: 0-200, 900; 201-300, 900; 301-400, 1,050; 401-500, 1,200; 501-600, 1,350; 601-700, 1,500. Table I, Estimated Sewage Flows. Residences, single or multiple family per dwelling unit: 1 Bedroom with 750 square feet or less of building area, 100; 2 Bedrooms with 751-1,200 square feet of building area, 200; 3 Bedrooms with 1,201-2,250 square feet of building area, 300; 4 Bedrooms with 2,251-3,300 square feet of building area, 400. For each additional bedroom or each additional 750 square feet of building area or fraction thereof in a dwelling unit, system sizing shall be increased by 60 gallons per dwelling unit. | The state's site |
| Georgia | Ga. Comp. R. & Regs. 511-3-1-.05(3)Georgia Department of Public Health | Capacity. The liquid capacity of septic tanks for single family dwellings shall be one thousand gallons for one, two, three or four bedrooms and 250 additional gallons for each bedroom over four. Septic tank capacity shall be increased by (50%) if a garbage grinder is to be used. | The state's site |
| Hawaii | Hawaii Administrative Rules § 11-62-33.1Hawaii Department of Health | The following schedule shall apply to septic tank sizing: No. of Bedrooms, Minimum Capacity (Gallons): 4 or less, 1000; 5, 1250. | The state's site |
| Idaho | IDAPA 58.01.03, section 007, subsection 08.aIdaho Department of Environmental Quality | Tanks serving single dwelling units. The minimum tank capacity is one thousand (1,000) gallons. For each bedroom over four (4) in a dwelling unit, add two hundred fifty (250) gallons. | Internet Archive copy of 2026-03-12 |
| Illinois | 77 Illinois Administrative Code 905, Appendix A, Illustration FIllinois Department of Public Health | Section 905.ILLUSTRATION F Minimum Volumes for Septic Tanks Serving Residential Units. Number of Bedrooms; Minimum Liquid Capacity of Tank (Gallons); Minimum Liquid Capacity of Tank (Gallons) When Garbage Grinder Is Used: 2 or less, 750, 1125; 3, 1000, 1500; 4, 1250, 2000; 5, 1500, 2200; 6, 1750, 2600; 7, 2000, 3000. | Internet Archive copy of 2026-06-09 |
| Indiana | 410 IAC 6-8.3-60(c), Table IIIIndiana Department of Health | Every septic tank shall have a minimum capacity below the water line as specified in Table III as follows: Number of Bedrooms in Dwelling, Capacity of Tank in Gallons: 2 or less, 750; 3, 1,000; 4, 1,250; 5, 1,500; 5 +, 1,500 plus 300 multiplied by the number of bedrooms over 5. | Internet Archive copy of 2025-11-01 |
| Iowa | Iowa Administrative Code 567—69.8(2)"a"Iowa Department of Natural Resources | Minimum capacity. The minimum liquid-holding capacity shall be as specified in the following table (capacity may be obtained by using one or more tanks): Up to and including 3-bedroom homes 1,250 gal. 4-bedroom homes 1,500 gal. 5-bedroom homes 1,750 gal. 6-bedroom homes 2,000 gal. | Internet Archive copy of 2025-02-08 |
| Kansas | KDHE Bulletin 4-2, Minimum Standards for Design and Construction of Onsite Wastewater Systems (March 1997), Table 7, applied under K.A.R. 28-5-6 to 28-5-9Kansas Department of Health and Environment | The minimum septic tank capacity is two times the daily wastewater flow using 150 gallons per bedroom or 1,000 gallons, whichever is larger. See Table 7 for minimum tank sizes. Tanks sized at three times daily flow are recommended and shall be required when garbage disposals are used. Table 7, Septic Tank Capacity (gallons), Minimum: 1–3 bedrooms, 1,000; 4, 1,200; 5, 1,500. For each additional bedroom, add 300 gallons to the minimum value and 450 gallons to the recommended value. | The state's site |
| Kentucky | 902 KAR 10:085, Table 2 (Minimum Capacity of Pretreatment Units)Kentucky Cabinet for Health and Family Services | A septic tank in a single-family residence on-site sewage disposal system shall meet the minimum working liquid capacities in paragraphs (a) to (c) of this subsection, based on the number of bedrooms involved. Number of Bedrooms, Gallon Capacity (Without Garbage Disposal), Gallon Capacity (With Garbage Disposal): 3 or less, 1,000, 1,250; 4, 1,250, 1,500; 5, 1,500, 1,750; Each Additional, 250, 250. | Internet Archive copy of 2026-10-03 |
| Louisiana | La. Admin. Code tit. 51, pt. XIII, § 715(D), with the sewage loading criteria of § 1501(A)Louisiana Department of Health, Office of Public Health | The minimum total septic tank liquid capacity required is 2 1/2 times the estimated average daily design flow. Sewage loading criteria for determining the average daily design flow and organic loading are contained in Chapter 15 of this Part. One-bedroom residences may, however, utilize a 500 gallon tank. NOTE: The minimum allowable total septic tank volume for all applications is 500 gallons. Chapter 15, Sewage Loading Criteria, § 1501. Individual Homes/Mobile Homes (where individual sewage technology is utilized. For each additional bedroom add 100 gpd), daily average flow, gallons per day: 250, one bedroom; 300, two bedrooms; 400, three bedrooms. | Internet Archive copy of 2024-12-02; § 715(D) read again in the department's file 8145.pdf, copy of 2026-07-01 |
| Maine | 10-144 CMR ch. 241, § 7(G)(1), Table 7AMaine Department of Health and Human Services, Maine Center for Disease Control and Prevention | The minimum liquid capacity of the septic tank(s) serving 1 to 3-family dwelling units must meet the capacity requirements of Table 7A for each dwelling unit. Table 7A, Septic Tank Capacity for Dwelling Units. Number of bedrooms per Unit, Minimum septic tank liquid capacity per Unit: 1 Bedroom, 750 gallons; 2 Bedrooms, 750 gallons; 3 Bedrooms, 1,000 gallons; 4 Bedrooms, 1,000 gallons; 5 Bedrooms, 1,250 gallons; For each additional, 250 gallons per bedroom. | Internet Archive copy of 2025-10-31 |
| Maryland | COMAR 26.04.02.05(D)Maryland Department of the Environment | Residential Septic Tank Size Criteria. Septic tanks serving a residential use, not requiring a BAT system, shall meet the following criteria and tables. This table provides for use of garbage disposal units, automatic clothes washers, and other household appliances. Number of Bedrooms, Minimum Septic Tank Capacity Below Outlet: 3 or less, 1,000 gallon; 4, 1,250 gallons; For each additional bedroom, add 250 gallons. | The state's site |
| Massachusetts | 310 CMR 15.223(1)(a) (Title 5), with the design flow of 310 CMR 15.203(2)Massachusetts Department of Environmental Protection | For a single family dwelling unit with a design flow of less than 1,000 gallons per day, a minimum effective liquid capacity of 200% of the design flow or a minimum hydraulic detention flow of 48 hours, whichever is greater, shall be required. In no case shall the effective liquid capacity of the tank as measured below the outlet invert elevation be less than 1,500 gallons. System sewage flow design criteria (310 CMR 15.203): Family Dwelling, Single, per bedroom, 110 gallons per day; minimum allowable for system design, 330. | The state's site |
| Michigan | Michigan Department of Environment, Great Lakes, and Energy, Michigan Guide to Environmental Regulations, Chapter 3 (Wastewater), Onsite Wastewater ProgramMichigan Department of Environment, Great Lakes, and Energy | Individual septic systems for homeowners are typically permitted and inspected by the local health department that covers the area where the home is located. | Internet Archive copies of 2026-06-21 (the page), 2026-06-06 (the department's septic FAQ) and 2025-06-13 (the guide) |
| Minnesota | Minnesota Rules, part 7080.1930, subpart 1, Table VMinnesota Pollution Control Agency | The liquid capacity of septic tanks must be at least as large as the liquid capacities given in Table V. Table V. Number of bedrooms, Septic tank liquid minimum capacities (gallons): 3 or less, 1,000; 4 or 5, 1,500; 6 or 7, 2,000; 8 or 9, 2,500. | The state's site |
| Mississippi | Mississippi State Department of Health, Individual Onsite Wastewater Disposal Design Standard (Chapter 5), Rule 5.1.9Mississippi State Department of Health | Rule 5.1.9. Septic Tank Sizing: The effective liquid capacity of septic tanks for dwellings shall be based on the number of bedrooms proposed or anticipated as shown in the table below. Number of Bedrooms; Minimum Effective Liquid Capacity (gallons) without baffle or effluent filter; with baffle or effluent filter: 2 or less, 750, 750; 3, 900, 900; 4, 1200, 1000; 5, 1500, 1250; 6, 1800, 1500. For each additional bedroom add 260 gallons. For each additional occupant over 2 per bedroom add 130 gallons. | The state's site |
| Missouri | 19 CSR 20-3.060(4)(B)16, Table 4Missouri Department of Health and Senior Services | The liquid capacity of a septic tank serving a dwelling shall be based upon the number of bedrooms contemplated in the dwelling served and shall be at least as large as the capacities given in Table 4. Table 4—Dwelling Septic Tank Capacity. Number of Bedrooms, Minimum Liquid Capacity (gallons): 1–3, 1000; 4, 1250; 5, 1500. These figures provide for use of garbage grinders, automatic clothes washers and other household appliances. For six (6) or more bedrooms, the septic tank shall be sized on the basis similar to an establishment. | Internet Archive copy of 2025-08-01 |
| Montana | Circular DEQ-4, Montana Standards for Subsurface Wastewater Treatment Systems (2023 edition), section 5.1.6.2(A)Montana Department of Environmental Quality | Residential septic tank capacity must be sized in accordance with the number of bedrooms as described below: 1. For 1 to 3 bedrooms, the minimum capacity is 1,000 gallons per living unit; 2. For 4 to 5 bedrooms, the minimum capacity is 1,500 gallons per living unit; 3. For 6 to 7 bedrooms, the minimum capacity is 2,000 gallons per living unit; 4. For 8 or more bedrooms, the minimum capacity is 2,000 gallons per living unit plus 250 gallons for each bedroom greater than 7 bedrooms. | The state's site |
| Nebraska | Nebraska Septic Tank and Subsurface Leach Field General Permit GTS220000 (June 27, 2022) under Title 124, section III.H, Table 3, with the design flow of section III.B, Table 1Nebraska Department of Water, Energy, and Environment | The minimum septic tank capacity for a single family or multi-family dwelling must be determined using the design flow and the tank capacity listed in Table 3. For a single-family dwelling, the design flow shall not be less than 100 gallons per day plus 100 gallons per day per bedroom. Table 3 - Minimum Septic Tank Capacity for a Dwelling. Design Flow in Gallons per Day; Septic Tank Capacity in Gallons For Dwelling without a Garbage Grinder or a Large Capacity Tub: 200, 1,000; 300, 1,000; 400, 1,000; 500, 1,250; 600, 1,500; 700, 1,750. | Internet Archive copy of 2026-06-09 |
| Nevada | NAC 444.8306(1)Nevada State Board of Health | The minimum capacity for a septic tank that serves a single-family dwelling is based on the number of bedrooms in the dwelling, and is determined as follows: Number of Bedrooms, Minimum Liquid Capacity of Tank (in Gallons): 3 or less, 1,000; 4, 1,200; 5 or 6, 1,500. If the single-family dwelling has more than six bedrooms, 150 gallons for each additional bedroom must be added to 1,500 gallons. | Internet Archive copy of 2025-01-15 |
| New Hampshire | N.H. Code of Administrative Rules, Env-Wq 1010.01New Hampshire Department of Environmental Services | For a single-family residence having no more than 4 bedrooms, minimum septic tank liquid capacity shall be 1,250 gallons. For each additional bedroom up to 10, the liquid capacity of the septic tank shall be increased by 250 gallons per bedroom. | Internet Archive copy of 2025-05-29 |
| New Jersey | N.J.A.C. 7:9A-8.2(b)1New Jersey Department of Environmental Protection | When serving single family dwelling units, septic tanks shall have the minimum capacity of 250 gallons per bedroom. Expansion attics shall be considered additional bedrooms. In no case shall the capacity be less than 1000 gallons. | Internet Archive copy of 2026-01-18 |
| New Mexico | 20.7.3.201(Q) NMAC, Table 201.2New Mexico Environment Department | The minimum liquid capacity of a septic tank shall be determined as follows: (1) for residential units, the liquid capacity shall be based on the number of bedrooms using Table 201.2. Table 201.2: Capacity of septic tanks. Single family dwellings, number of bedrooms; Minimum septic tank capacity in gallons: 1, 750; 2 - 3, 1000; 4, 1200; 5 - 6, 1500; 7 - 9, 2000. | The state's site |
| New York | 10 NYCRR Appendix 75-A, section 75-A.6(a)(1) and Table 3New York State Department of Health | Septic tank capacities shall be based upon the number of household bedrooms. An expansion attic shall be considered as an additional bedroom. Table 3 specifies minimum septic tank capacities and minimum liquid surface areas. Table 3, Minimum Septic Tank Capacities. Number of Bedrooms, Minimum Tank Capacity (gallons): 1, 2, 3, 1,000; 4, 1,250; 5, 1,500; 6, 1,750. Tank size requirements for more than six bedrooms shall be calculated by adding 250 gallons and seven square feet of surface area for each additional bedroom. A garbage grinder shall be considered equivalent to an additional bedroom for determining tank size. | The state's site |
| North Carolina | 15A NCAC 18E .0801(a), Table XIVNorth Carolina Department of Health and Human Services | The minimum capacity of any septic tank serving an individual dwelling unit with five bedrooms or less shall be sized as set forth in Table XIV. Table XIV. Minimum septic tank liquid capacity for dwelling units. Number of bedrooms, Minimum liquid capacity in gallons: 4 or less, 1,000; 5, 1,250. | The state's site |
| North Dakota | N.D. Admin. Code § 62-03.1-03-07(1), table Capacity of Septic TanksNorth Dakota State Plumbing Board | Liquid capacity. The liquid capacity of all septic tanks shall conform to the tables contained in subsection 7 of section 62-03.1-03-03 and this subsection as determined by the number of bedrooms or apartment units in dwelling occupancies. Single-Family Dwellings, Number of Bedrooms, Minimum Septic Tank Working Capacity in Gallons: 1-3, 1000; 4, 1200; 5 or 6, 1500; 7 or 8, 2000. Extra bedroom, 150 gallons each. | The state's site |
| Ohio | Ohio Administrative Code 3701-29-12(C)(1)Ohio Department of Health | Minimum liquid capacities: (a) One to two bedrooms - one thousand gallons in one or two compartments. (b) Three bedrooms - one thousand five hundred gallons in two tanks or compartments. (c) Four to five bedrooms - two thousand gallons in two tanks or compartments. (d) Six or more bedrooms - two thousand five hundred gallons plus an additional two hundred fifty gallons of tank capacity for each bedroom in two tanks or compartments. | Internet Archive copy of 2026-06-07 |
| Oklahoma | Oklahoma Administrative Code 252:641-7-4(a)Oklahoma Department of Environmental Quality | A septic tank used in an individual on-site sewage treatment system for a residential unit with four (4) or fewer bedrooms shall have a liquid capacity of at least one thousand (1,000) gallons. An additional two hundred and fifty (250) gallons of capacity must be added for each additional bedroom. | Internet Archive copy of 2025-06-20 |
| Oregon | OAR 340-071-0220(3)(a)(C)Oregon Department of Environmental Quality | The capacity of a septic tank that serves a single family dwelling must be based on the number of bedrooms in the dwelling. For a dwelling with 4 or fewer bedrooms, the tank capacity must be at least 1,000 gallons. Septic tank capacity must be at least 1,500 gallons for dwellings with more than 4 bedrooms. | Internet Archive copy of 2025-09-02 |
| Pennsylvania | 25 Pa. Code § 73.31(a)Pennsylvania Department of Environmental Protection | The minimum liquid septic tank capacity for any installation is 900 gallons. For single-family dwelling units, not served by a community onlot system, a minimum daily flow of 400 gpd shall be used to determine required septic tank capacity. This figure shall be increased by 100 gallons for each additional bedroom over three. The minimum septic tank capacity shall be calculated from the following table using estimated sewage flows from paragraph (2): 0—500 gallons per day, (3.5 x flow exceeding 400 gpd) + (900); 500—5,000, (1.50 x flow exceeding 500 gpd) + (1,250). | The state's site |
| Rhode Island | 250-RICR-150-10-6, § 6.27(B)(1)Rhode Island Department of Environmental Management | Residential Dwellings – The required minimum liquid capacity of a septic tank, below the flow line, shall be based on the number of bedrooms in the dwelling. For three (3) bedrooms or less the minimum capacity shall be one thousand (1,000) gallons. For each additional bedroom, add two hundred fifty (250) gallons. A garbage grinder or a one hundred (100) gallon or greater tub will each require the septic tank capacity be increased by two hundred fifty (250) gallons. | The state's site |
| South Carolina | S.C. Code Regs. 61-56, section 201.1(3)South Carolina Department of Environmental Services | No septic tank shall be installed which has a net liquid capacity of less than one thousand (1000) gallons. Such tanks shall be sufficient to serve dwellings of four (4) bedrooms or less. Two hundred fifty (250) gallons additional capacity shall be required for each bedroom over four (4). | Internet Archive copy of 2026-08-05 |
| South Dakota | ARSD 74:53:01:25(1)South Dakota Department of Agriculture and Natural Resources | All septic tanks receiving wastewater flows of 750 gallons per day or less shall have a minimum capacity of at least 1,000 gallons of liquid before there will be an overflow into the septic tank outlet. When a housing unit or units served by a septic tank contains more than three bedrooms, each bedroom in excess of three shall require an additional 250-gallon increase in the capacity of the septic tank beyond the 1,000 gallons. If a septic tank receives wastes from a garbage disposal, the overall capacity of the tank shall be increased by an additional 20 percent. | The state's site |
| Tennessee | Tenn. Comp. R. & Regs. 0400-48-01-.08(1)Tennessee Department of Environment and Conservation | For residences, the liquid capacity of the septic tank shall be based on the following: Number of Bedrooms, Septic Tank Capacity: 2 or less, 750 gallons; 3, 900 gallons; 4, 1000 gallons. For each additional bedroom, add two hundred fifty (250) gallons. | The state's site |
| Texas | 30 Texas Administrative Code § 285.91(2), Table II, with the usage rates of § 285.91(3), Table IIITexas Commission on Environmental Quality | SEPTIC TANK MINIMUM LIQUID CAPACITY. A. Determine the applicable wastewater usage rate (Q) in TABLE III of 30 TAC Chapter 285. B. Calculate the minimum septic tank volume (V) as follows: 1. For Q equal to or less than 250 gal/day: V = 750 gallons 2. For Q greater than or equal to 251 gal/day but less than or equal to 350 gal/day: V = 1000 gallons 3. For Q greater than or equal to 351 gal/day but less than or equal to 500 gal/day: V = 1250 gallons | Internet Archive copies of 2024-08-11 and 2024-08-14 (the Texas Register's files for Table II and Table III) |
| Utah | Utah Admin. Code R317-4-6(7)(b)Utah Department of Environmental Quality, Division of Water Quality | The capacity of a septic tank that serves a single-family dwelling shall be based on the number of bedrooms that can be anticipated in the dwelling served, including the unfinished space available for conversion as additional bedrooms. Unfinished basements shall be counted as a minimum of one additional bedroom. The minimum liquid capacity of the tank shall be 1,000 gallons for up to three bedroom homes. The minimum liquid capacity of the tank shall be 1,250 gallons for four bedroom homes. Two hundred fifty gallons per bedroom shall be added to the liquid capacity of the tank for each additional bedroom over four bedrooms. | The state's site |
| Vermont | Vermont Wastewater System and Potable Water Supply Rules (effective November 6, 2023), § 1-908(a), Table 9-1, with the design flow of § 1-803(c) and (d)Vermont Department of Environmental Conservation | A septic tank shall be sized for the minimum capacity established in Table 9-1. Table 9-1, Minimum Capacities for Septic Tanks. Design Flow, Gallons Per Day; Liquid Capacity Below the Bottom of the Outlet: 560 or less, 1000 gallons; Greater than 560 – less than 6500, 2 times design flow. The septic tank capacity shall be increased by a minimum of 50 percent above the capacities in Table 9-1 if the building or structure to be served by the wastewater system will include a garbage disposal. | Internet Archive copy of 2025-02-24 |
| Virginia | 12VAC5-610-815(A), Table 5.2Virginia Department of Health | The minimum hydraulic detention time shall be 48 hours based on daily design flow. In no case shall the septic tank capacity be less than 750 gallons. Table 5.2 contains the minimum required septic tank capacities for dwelling units. Table 5.2. Septic Tank Capacities for Dwelling Units. No. of Bedrooms, Approximate Tank Volume in Gallons: 1, 750; 2, 750; 3, 900; 4, 1200; 5, 1500. | Internet Archive copy of 2026-04-13 |
| Washington | WAC 246-272A-0232(2)(a), Table VIIWashington State Department of Health | Have the following minimum liquid volumes: (a) For a single-family residence use Table VII: Required Minimum Liquid Volumes of Septic Tanks. Number of Bedrooms ≤4: 1,000. Each additional bedroom: 250. | The state's site |
| West Virginia | W. Va. Code R. § 64-47-6.4.aWest Virginia Department of Health, Bureau for Public Health | Liquid capacities for tanks serving single-family dwellings shall be in accordance with the following: For four or fewer bedrooms, the minimum tank capacity shall be 1,000 gallons; and For each additional bedroom, the minimum tank capacity shall be 250 gallons per bedroom. | The state's site |
| Wisconsin | Wis. Admin. Code SPS 383.43(2) and (3) (design flow); Wisconsin POWTS Inspector's Handbook (2022), chapter 10Wisconsin Department of Safety and Professional Services. The department's handbook: dsps.wi.gov, Programs, POWTS, POWTS Inspector's Handbook 2022 | In order to accommodate peak wastewater flow, the design wastewater flow of a POWTS shall equal at least 150% of the estimated daily flow generated from the source or sources, unless otherwise approved by the department. Handbook: Capacity conforms to permit. Minimum septic tank capacity for a 3-year service cycle may be calculated by multiplying the design flow by a factor of 2.088. | Internet Archive copies of 2026-07-26 (chapters SPS 383 and SPS 384) and 2026-01-13 (the department's handbook) |
| Wyoming | Wyoming Water Quality Rules, Chapter 25, Section 10(a)(iii)(A)Wyoming Department of Environmental Quality, Water Quality Division. Environmental Quality, Dept. of; Water Quality; Chapter 25 (reference number 020.0011.25.06292018, in effect since June 29, 2018) | The minimum liquid volume of a septic tank shall be 1000 gallons for residences up to a four (4) bedroom capacity. Additional capacity of 150 gallons per bedroom shall be provided for each bedroom over four (4). | The state's site |
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