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Frost data
How deep are water lines buried?
The short answer
A water service line has to be buried at least 12 inches down, and at least 6 inches below the local frost line, whichever is deeper. That is the model code rule in one sentence: Water service pipe shall be installed not less than 12 inches (305 mm) deep and not less than 6 inches (152 mm) below the frost line.
Because the frost line changes by state and by jurisdiction, so does the answer. Of the 50 states, 38 land on the twelve-inch floor because their published frost depth is at or below six inches or is not published at all, while Minnesota and Vermont work out to 66 inches. The state table is below, and the ZIP lookup gives you the figure for one address.
Minimum burial depth for your ZIP
The rule
Why it is written as frost depth plus a floor
The rule has two halves because it is solving two problems. Burying the pipe below the frost line keeps the water in it from freezing, expanding and splitting the pipe in a cold winter, and the code asks for six inches of clearance rather than merely getting under the line. The twelve-inch floor applies where there is no meaningful frost line to sit below, and it is there to keep the pipe out of reach of a shovel, a rototiller, a tree root and the daily temperature swing at the surface.
That is also why the deepest states in the table are the ones with the longest winters rather than the ones at the highest latitudes. A design frost depth reflects how long a winter stays cold as much as how cold it gets, so a high-elevation interior state can require more than a coastal state further north. 2021 International Residential Code, Section P2603.5 (Freezing), ICC free code viewer.
Two things the code minimum does not settle. Your local jurisdiction can require more, and several do. And your water utility writes its own construction specification for the service it owns, which is frequently deeper than the residential code minimum. Two examples of how much further a utility can go:
- Metro Nashville and Davidson County, water service installation: requires 24 inches of cover over a residential water service, double the model-code floor, in a state that publishes no frost figure at all.
- City of Spokane and Spokane County, joint frost depth policy: sets an official 24-inch frost depth for the city and county together, so that two adjoining jurisdictions inspect to one number.
All 50 states
Minimum burial depth by state
The published code frost depth, and the burial minimum it implies under the model-code rule.
| State | Code frost depth | Minimum water line burial | Basis | Where it comes from |
|---|---|---|---|---|
| Alabama | set locally | 12 in | local jurisdiction (varies)City of Mobile, AL 12 in; Mobile County, AL (unincorporated) 12 in | City of Mobile, Ordinance Adopting the 2021 IRC (Table R301.2) |
| Alaska | set locally | 12 in | local jurisdiction (varies)Municipality of Anchorage, AK 42 in | Municipality of Anchorage, Chapter 23.85 local amendments to t… |
| Arizona | set locally | 12 in | local jurisdiction (varies)City of Phoenix, AZ 0 in; City of Flagstaff, AZ 30 in | City of Phoenix 2018 IRC Amendments (Table R301.2(1)) |
| Arkansas | set locally | 12 in | local jurisdiction (varies)City of Little Rock, AR 12 in | City of Little Rock Codes & Design Criteria |
| California | set locally | 12 in | local jurisdiction (varies)Truckee/Tahoe area, Placer County (5,001,7,000 ft) 18 in; Truckee/Tahoe area, Placer County (7,001,8,000 ft) 24 in | California Building Standards Commission (Dept. of General Ser… |
| Colorado | set locally | 12 in | local jurisdiction (varies)City and County of Denver 36 in; Colorado Springs / El Paso County (Pikes Peak Regional Building Dept.) 30 in | 2022 Denver Building & Fire Code (official), frost protection … |
| Connecticut | 42 in | 48 in | state code amendment | 2022 Connecticut State Building Code (w/ Errata #1), Amd 1809.… |
| Delaware | set locally | 12 in | local jurisdiction (varies)New Castle County (unamended IRC baseline) 12 in; Sussex County, DE 24 in | New Castle County Dept. of Land Use, Single-Family Dwelling Pl… |
| Florida | 0 in | 12 in | state code amendment | 2023 Florida Building Code, Residential, 8th Ed., Ch. 4 Founda… |
| Georgia | set locally | 12 in | local jurisdiction (varies)Macon-Bibb County, GA 18 in; City of Sandy Springs, GA 12 in | 2018 IRC with Georgia Amendments, Ch. 3, Table R301.2(1) footn… |
| Hawaii | set locally | 12 in | local jurisdiction (varies) | Hawaii State Building Code Council, Hawaii State Residential C… |
| Idaho | set locally | 12 in | local jurisdiction (varies)City of Boise (local IBC/IRC amendment, eff. 2021) 24 in; Kootenai County (local IBC/IRC amendment) 24 in | Idaho Administrative Code IDAPA 24.39.30, Rules of Building Sa… |
| Illinois | set locally | 12 in | local jurisdiction (varies)City of Chicago 42 in; Village of Flossmoor 42 in; City of Peoria, IL 36 in | City of Chicago Dept. of Buildings, Porch Design & Constructio… |
| Indiana | 24 to 36 in | 42 in | state code amendmentWayne County, IN 30 in; Wells, White and Whitley Counties, IN 36 in | Indiana Administrative Code 675 IAC 14-4.4-5, Table R301.2(1),… |
| Iowa | set locally | 12 in | local jurisdiction (varies)City of Des Moines, IA 42 in; Johnson County, IA 42 in | City of Des Moines, Construction Codes (Design Criteria / Loca… |
| Kansas | set locally | 12 in | local jurisdiction (varies)City of Manhattan, KS 34 in; Johnson County, KS 36 in | City of Manhattan, KS, Climate & Geographic Design Criteria |
| Kentucky | 24 to 33 in | 39 in | state code amendmentMartin, Pike, Knott, Letcher, Floyd Counties, KY 33 in; All other Kentucky counties (default) 24 in | 2018 Kentucky Residential Code, 2nd Edition (Kentucky Dept. of… |
| Louisiana | 12 in | 18 in | state code amendment | LSUCCC, Uniform Construction Codes and Amendments (eff. 01-01-… |
| Maine | set locally | 12 in | local jurisdiction (varies)Bangor, ME 60 in; Brewer, ME 60 in | City of Bangor, Maine, Building Codes |
| Maryland | set locally | 12 in | local jurisdiction (varies)Montgomery County, MD 30 in; Baltimore County, MD 30 in | Montgomery County MD, guidelines for building residential deck… |
| Massachusetts | 48 in | 54 in | state code amendment | 780 CMR 51.00 Massachusetts Residential Code, Ch. 3 Building P… |
| Michigan | 42 in | 48 in | state code amendment | Michigan LARA, 2021 Michigan Residential Code, Rule 516 (R 408… |
| Minnesota | 42 to 60 in | 66 in | state code amendmentZone I (33 northern counties incl. St. Louis, Itasca, Beltrami, Cook, Koochiching) 60 in; Zone II (48 central/southern counties incl. Hennepin, Ramsey, Anoka, Washington, Winona) 42 in | Minnesota Rule 1303.1600, Footing Depth for Frost Protection (… |
| Mississippi | set locally | 12 in | local jurisdiction (varies) | jurisdiction sources only, listed above |
| Missouri | set locally | 12 in | local jurisdiction (varies)Springfield, MO (city ordinance) 24 in; Missouri, north of Hwy 36 (state agency reference map) 25 in; Missouri, south of I-44 (state agency reference map) 12 in | Missouri Public Service Commission, 2016 State of Missouri Fro… |
| Montana | 36 to 48 in | 54 in | state code amendment | Montana Dept. of Labor & Industry, Building Codes Bureau, Buil… |
| Nebraska | set locally | 12 in | local jurisdiction (varies)City of Lincoln / Lancaster County, NE 36 in | Lincoln Municipal Code §20.12.140, Table R301.2 Amended (Clima… |
| Nevada | set locally | 12 in | local jurisdiction (varies)Washoe County / Reno, NV 24 in; Clark County / Las Vegas Valley, NV (elevations below 1,600 ft) 12 in | Washoe County Building Division, Construction Design Requireme… |
| New Hampshire | set locally | 12 in | local jurisdiction (varies)City of Manchester, NH 48 in | City of Manchester, NH, Locally adopted Building Code / Table … |
| New Jersey | set locally | 12 in | local jurisdiction (varies) | N.J.A.C. 19:6-2.3, Depth of Foundations (NJ UCC Building Subco… |
| New Mexico | set locally | 12 in | state code amendmentStatewide (2021 NM Residential Code, 14.7.3.12 NMAC §R403.1.4) 12 in; City of Albuquerque, NM 16 in; City of Farmington, NM 24 in | New Mexico Regulation & Licensing Dept., Construction Industri… |
| New York | set locally | 12 in | local jurisdiction (varies)Town of Smithtown, Suffolk County, NY 36 in; Town of Pittsford, Monroe County, NY 42 in; Town of Enfield, Tompkins County, NY 42 in | NYS Dept. of State, Division of Building Standards and Codes, … |
| North Carolina | set locally | 12 in | local jurisdiction (varies) | NC Office of State Fire Marshal, 2018 NC Plumbing Code Amendme… |
| North Dakota | set locally | 12 in | local jurisdiction (varies)City of Fargo, ND 52 in; City of Bismarck, ND 48 in | North Dakota Department of Commerce / State Building Code Book… |
| Ohio | set locally | 12 in | local jurisdiction (varies)City of Toledo, OH 36 in; Lucas County, OH 36 in; City of Stow, OH (Summit County) 36 in; City of Dayton, OH 32 in | Ohio Administrative Code 4101:8-3-01, Table 301.2(1) Climatic … |
| Oklahoma | set locally | 12 in | local jurisdiction (varies)City of The Village, OK (Oklahoma County) 18 in | Oklahoma Uniform Building Code Commission (OUBCC) |
| Oregon | 12 to 24 in | 30 in | state code amendmentMultnomah County (below 2,500 ft elevation) 18 in; Baker County 24 in; Benton, Clackamas, Lane Counties (Willamette Valley) 12 in | 2023 Oregon Residential Specialty Code, Summary of Amendments,… |
| Pennsylvania | set locally | 12 in | local jurisdiction (varies)City of Erie, PA 48 in; City of Allentown, PA 36 in; City of Lancaster, PA 36 in | PA Department of Labor & Industry, Uniform Construction Code (… |
| Rhode Island | 40 in | 46 in | state code amendmentNew Shoreham (Block Island) â statewide code exception 30 in | Rhode Island State Building Code SBC-2 (RI One & Two Family Dw… |
| South Carolina | set locally | 12 in | local jurisdiction (varies)Anderson County, SC 12 in; City of Charleston, SC 0 in; York County, SC 12 in | South Carolina 2021 Code Modifications (LLR Building Codes Cou… |
| South Dakota | set locally | 12 in | local jurisdiction (varies)Hartford / Minnehaha County, SD 42 in; City of Madison, SD 42 in | City of Hartford, SD Building Handbook |
| Tennessee | set locally | 12 in | local jurisdiction (varies)Knox County, TN 12 in; Nashville-Davidson County, TN (water-service cover, not footing depth) 24 in | TN Dept. of Commerce & Insurance, Div. of Fire Prevention â … |
| Texas | set locally | 12 in | local jurisdiction (varies)City of Dallas, TX 6 in; City of Lubbock, TX 12 in | City of Dallas Ordinance 23-0471, amendments to the 2021 IRC, … |
| Utah | set locally | 12 in | local jurisdiction (varies)St. George, UT (Washington County) 12 in; Duchesne County, UT 30 in; Greater Salt Lake Municipal Services District, UT 30 in | Utah Division of Administrative Rules â Bulletin filing for … |
| Vermont | 60 in | 66 in | state code amendment | 2025 Vermont Fire & Building Safety Code (Division of Fire Saf… |
| Virginia | set locally | 12 in | local jurisdiction (varies)Shenandoah County, VA 24 in; Fairfax County, VA 24 in | Virginia DHCD â Virginia Uniform Statewide Building Code (US… |
| Washington | set locally | 12 in | local jurisdiction (varies)City of Spokane / Spokane County, WA (joint policy) 24 in; City of Everett, WA 18 in | WAC 51-51-0301 (WA amendments to IRC R301.2) â frost-line cr… |
| West Virginia | set locally | 12 in | local jurisdiction (varies)Morgantown, WV 30 in | West Virginia State Fire Commission, 87 CSR 4 State Building C… |
| Wisconsin | 48 in | 54 in | state code amendment | Wisconsin Legislature â Wis. Admin. Code SPS 321.16, "Frost … |
| Wyoming | set locally | 12 in | local jurisdiction (varies)Casper / Natrona County, WY 36 in; Teton County, WY 34 in | City of Casper, WY â Engineering and Climatic Design Criteri… |
“Set locally” is the honest answer for most of the country: the state adopts a model code and leaves the frost-line cell of Table R301.2(1) for the building department that issues your permit to fill in. Where that is the case we list the figures real jurisdictions publish rather than printing a number the state does not. Confirm your own figure with your local building department before you dig or pour.
The burial column is arithmetic on the state figure, not a separate citation: it is the deeper of the state code frost depth plus six inches and the twelve-inch model-code floor. Where a state publishes no frost figure the column shows the floor, and the real requirement is whatever your jurisdiction has adopted. Where a state plumbing code adds its own cover requirement, that is noted on the state page.
What it means
When burial depth turns into a bill
Depth is the reason a water service replacement is priced by the foot and the reason the quote changes when the line runs under a driveway. Trenching four feet through frozen ground in Minnesota is a different job from trenching twelve inches in Florida, and the same hundred feet of pipe costs very different money in the two places.
It also explains where freezes actually happen. A properly buried service line rarely freezes. The pipe that freezes is the one above ground in an unheated crawl space, or the last few feet where the service comes through the foundation wall. That is why the temperature threshold and what to do when a pipe freezes matter more for most homeowners than the depth in the yard. If a line has already split, our burst pipe repair cost and whole-house repipe cost pages cover what the work runs.
For the footing side of the same number, and a map, see frost line depth by state.
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Common questions
Water line depth questions
How deep is the water line coming into my house?
At least six inches clear of your local frost line, and at least 12 inches down anywhere in the country. In a cold state that puts the service line four or five feet below the yard; in a warm state it can be a foot. Where it enters the house is the part worth knowing, because that penetration is often the coldest point on the whole run and the place a freeze starts. If you need the actual depth rather than the minimum, your water utility can usually tell you what it required when the service was installed.
How do I find buried water lines?
Call 811 before any digging, including a fence post or a mailbox. It is a free national service, the utilities send someone to mark their lines, and in most states using it is a legal requirement rather than a courtesy. The marks cover the utility-owned portion; the private line from the meter to your house is usually yours to locate, and a plumber with a line locator can trace it. Call 811 before you dig.
Are sewer lines deeper than water lines?
Usually, and for a different reason. A sewer line drains by gravity, so its depth is set by the slope it needs to reach the main rather than by frost. That is why a sewer lateral gets deeper the farther it runs from the house while a water service holds a fairly even depth. Codes also require horizontal separation between the two, so a plumber replacing one has to dig a fresh trench rather than reuse the other.
Does a water line have to be below the frost line?
Yes, and with clearance. The model code puts it plainly: Water service pipe shall be installed not less than 12 inches (305 mm) deep and not less than 6 inches (152 mm) below the frost line.
Both clauses bind. The six inches below the frost line is what protects the pipe in a cold state, and the twelve-inch floor is what applies in a state whose code frost depth is effectively zero and there is no frost line to sit below.
Can I bury a water line shallower if I insulate it?
That is a question for the building department that issues the permit, and the answer is often no for a service line. Some jurisdictions allow insulation or heat trace as an alternative in specific situations, and some do not allow any reduction of the buried depth at all. Doing it without checking risks a failed inspection now and a frozen service line later, and a service line that splits under a driveway is one of the more expensive repairs in residential plumbing.
Where these numbers come from
Each state frost figure carries its own source in the table above and on that state’s page. The burial column is derived from those figures under the model-code rule rather than separately cited, and we say so rather than dressing arithmetic up as a citation.
- Freeze dates and cold-night counts: NOAA NCEI U.S. Climate Normals, 1991 to 2020, annual and seasonal by station. Retrieved 2026-09-09. Field definitions are in the by-variable readme.
- ZIP code locations: U.S. Census Bureau 2023 ZIP Code Tabulation Area gazetteer, matched to the nearest station by great-circle distance.
- 2021 International Residential Code, Section P2603.5 (Freezing), ICC free code viewer The burial rule, quoted verbatim on this page.
- Call 811 before you dig The national one-call service for locating buried utilities before excavation.
- Metro Nashville and Davidson County, water service installation requires 24 inches of cover over a residential water service, double the model-code floor, in a state that publishes no frost figure at all.
- City of Spokane and Spokane County, joint frost depth policy sets an official 24-inch frost depth for the city and county together, so that two adjoining jurisdictions inspect to one number.
The full method, including how we pick a station and what we do when there is not one close enough, is on our methodology page.
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