Which plumbing code governs an Ohio house, who holds the license, and who inspects

The plumbing in an Ohio house is not governed by the residential code. The Residential Code of Ohio contains exactly one plumbing chapter, and that chapter's whole job is to hand the subject over to the Ohio Plumbing Code, the same document that governs the plumbing in a hospital or an office building. The two codes run on different clocks and use different section numbers, which is why a shower rule quoted from the model residential code usually does not exist in Ohio at all. This page follows the chain from the statute that creates both codes down to the shower valve, then out to the state license and to the office that does plumbing inspection in each Central Ohio county.

Last updated September 2026 · Code sections, statutes and county office pages are quoted as read September 2026 · No prices on this page; the Estimate Builder carries those · Part of the knowledge base

The plumbing in an Ohio house is governed by the plumbing code, not the residential code

Ohio does have a residential code, and it does cover your house. It is titled the Residential Code of Ohio for One-, Two-, and Three-Family Dwellings, it is built on the 2018 edition of the International Residential Code, and its scope reaches "every one-, two-, or three-family dwelling, any appurtenances connected or attached to such buildings," in alteration, repair and replacement as well as in new work. Its administration, building planning and plumbing chapters each carry a posted effective date of July 1, 2019. How houses came to be covered by a state code at all, after decades when Ohio's building code left them out, is on the page on who shaped Central Ohio houses. The Ohio plumbing act of 1896 and the Columbus office that inspected plumbing before it are on the page on how Columbus came to inspect its houses.

What surprises people is what its plumbing chapter does with the subject. There is exactly one of them, and section 2501.1 of it says the Ohio Plumbing Code "shall govern the installation, testing and operation of the plumbing in buildings" within the residential code's scope, subject to a short list of modifications. So a shower in a Clintonville bungalow answers to the same document as an office building. Franklin County Public Health says it from the administering end too: plan review and permits, it writes, "are required by the Ohio Plumbing Code for commercial and residential buildings."

Ohio never adopted the model residential code's plumbing chapters at all. The Ohio Administrative Code division holding the Residential Code of Ohio runs from chapter 1 through chapter 25 and then jumps to chapters 29, 34 and 44. Ask the state's own site for the chapter that would carry residential plumbing fixtures and it answers that no rule number corresponds to it. That is why the P27xx section numbers people quote for shower size and shower valves do not exist here.

The Ohio Plumbing Code is a set of rules in Ohio Administrative Code division 4101:3, and its administration chapter incorporates "the International Plumbing Code, 2021 edition, Chapters 2 through 15" by reference. The Board of Building Standards readopted that code effective March 1, 2024 and amended it again effective October 15, 2025. Set those beside the residential code's July 1, 2019 and the shape is plain: a 2019 residential code pointing at a plumbing code readopted and amended since.

Who writes these codes, and who adopts them

Both come from one statute. Ohio Revised Code section 3781.10 directs the Board of Building Standards to adopt building rules and says "the board shall incorporate those rules into separate residential and nonresidential building codes."

The same statute puts enforcement in local hands: "the board shall certify municipal, township, and county building departments" to enforce the codes, and it certifies separately for the residential and the nonresidential code, so a department may hold one and not the other. It then fixes what those departments enforce, saying "in no case shall any local code or regulation differ from the state" residential building code except in the narrow cases it names. So the code text is the same across Ohio even where the office administering it is not. Which Central Ohio suburbs and counties hold that certification, and which of them enforce plumbing locally rather than through a county health agency, is set out on the page about which building code a house was built under.

What the code requires of a shower in a house

These are the sections that decide what a shower in an Ohio house has to be, given with their numbers, because a number is what makes a claim checkable.

The valve, and the temperature limit

Ohio Plumbing Code section 412.3 requires a shower or tub-shower valve to be one of three kinds: "balanced-pressure, thermostatic or combination balanced-pressure/thermostatic valves that conform to the requirements of ASSE 1016" or a second named standard. It also requires the valve to be "equipped with a means to limit the maximum setting of the valve to 120" degrees Fahrenheit, field adjusted to the manufacturer's instructions, and says an in-line thermostatic valve may not be used to satisfy that. Ohio's amendments to the fixtures chapter do not touch 412.3. What the three types feel like in use is the valves page.

The size of the compartment

Section 421.4 sets two dimensions. A shower compartment "shall be not less than 900 square inches in interior cross-sectional area," and "shall be not less than 30 inches in least dimension," measured from the finished interior at the top of the threshold and carried up to a height not less than 70 inches above the shower drain outlet. An exception allows a least dimension of 25 inches where the compartment has "not less than 1,300 square inches of cross-sectional area," which is what permits a narrower compartment that is longer, the common shape when an alcove tub comes out. This is a least-dimension test, not the thirty-inch circle in the model residential code, whose plumbing chapters Ohio does not adopt. How the arithmetic lands in a small room is on the five-by-eight page.

The drain, the walls and the liner

Section 421.3 sets the shower waste outlet at "not less than 1 1/2 inches in diameter," with a removable strainer of not less than three inches. Traps, trap arms and venting belong to the house drains page.

The wall finish is one of the few plumbing-adjacent rules the residential code keeps for itself. Section 307.2 requires bathtub and shower floors, the walls above a bathtub with an installed shower head, and the walls in shower compartments to be finished with a nonabsorbent surface, and says "such wall surfaces shall extend to a height of not less than 6 feet" above the floor. Ohio drops the model code's R prefix, so it is 307.2 and not R307.2. The plumbing code states a parallel requirement at section 421.4.1 for smooth, corrosion-resistant and nonabsorbent waterproof materials, with heights of its own written differently.

The residential code also writes its own shower lining rule in place of the plumbing code's, requiring the liner to turn up on all sides "at least 2 inches" above the finished threshold level, to be fastened to an approved backing, and not to be nailed or perforated less than one inch above the finished threshold. The number that rule cites for the provision it replaces no longer matches the plumbing code's numbering, so read it by its words rather than its cross reference. Ohio's fixtures rule adds an exception saying "the shower liner test is not required for one-, two-, or three-family dwellings" unless the liner manufacturer's instructions require it.

Approval, and the short list that does not need one

The residential code says approval where local offices say permit. Section 105.1, headed "Approvals required," says an owner who intends to alter, repair or replace a plumbing system must first "make application to the residential building official of a certified residential building department."

Section 102.10 then exempts a short list. Among the items are "the clearance of stoppages or the repair of leaks in pipes, valves or fixtures," and the removal and reinstallation of water closets, on the condition that the repairs do not involve or require the replacement of more than one fixture or the rearrangement of valves, pipes or fixtures. The leak exemption stops where a concealed pipe has to be removed and replaced, which the section says is treated as new work. Read by its own words, work that rearranges fixtures sits outside that list.

The state license, and the line it does not cross

Ohio Revised Code section 4740.02 creates the Ohio Construction Industry Licensing Board inside the Department of Commerce. It has seventeen members and a five-member plumbing and hydronics section which, in the statute's words, "has primary responsibility for the licensure of plumbing contractors": one plumbing inspector, two plumbing contractors with no union affiliation, and two who are signatories to union agreements. The chapter's one dated hook is that initial appointments were to be made within ninety days after July 31, 1992.

The chapter issues five contractor types and nothing else: plumbing, electrical, heating and air conditioning, refrigeration and hydronics. There is no journeyman or apprentice credential anywhere in it. How the same chapter reaches the electrical trade, and why its credential is written around commercial work rather than houses, is on the bathroom electrical page.

Section 4740.06 sets what an applicant shows: at least eighteen years old, and work in the trade "not less than five years immediately prior to the date the application is filed," with two alternatives, being a currently registered engineer in this state with three years of business experience in the construction industry, or having other experience acceptable to the board's specialty section. The applicant must also "maintain contractor's liability insurance in an amount the appropriate specialty section" sets, and must pass the required examination. The statute names no insurance amount.

Section 4740.07 decides what a company's credential really is. The board issues and renews "all licenses under this chapter in the name of the individual," and that individual assigns the license to one contracting company, with work done under it treated as done under that person's personal supervision. A company's credential is a named person's credential.

The complication most homeowners never hear

Section 4740.01 defines a construction project as one involving a building subject to Ohio Revised Code chapter 3781, "but not an industrialized unit or a residential building as defined in section 3781.06." Section 3781.06 defines a residential building as a one-family, two-family or three-family dwelling house. The state's contractor licensure chapter is written around nonresidential work, and the Ohio Department of Commerce describes the board the same way in its own published material, as issuing licenses to commercial contractors in those five trades.

That is the state layer, and the city layer can differ. Under chapter 4114 of the city code, Columbus "requires and issues licenses for individuals who intend to work in the City" as a journeyperson plumber, a credential the state does not issue at all, and it issues a home improvement general contractor license for the repair, remodeling or alteration of existing one-, two- and three-family dwellings, for which the state chapter has no counterpart. The city also states that to work in Columbus as an electrical, heating and air conditioning, refrigeration, hydronics or plumbing contractor, an applicant must hold the state credential.

That is not an accident of drafting. Ohio Revised Code section 4740.12 says no political subdivision may adopt an ordinance requiring contractor registration and a registration fee unless the same ordinance also requires the state credential for that trade, while separately preserving local ordinances that register tradespersons. That pair is how a state credential written around nonresidential buildings reaches a house in Columbus: not through the state chapter, which excludes the house, but through the city's own ordinance.

Who inspects, and why the answer is an address

Ohio Revised Code chapter 3703 sets the default, and the default is not a county health department. Section 3703.01 directs the division of industrial compliance in the Department of Commerce to "inspect all nonresidential buildings within the meaning of section 3781.06." The chapter then steps that duty aside in two ways. One clause bars the division, boards of health of city and general health districts, and county building departments alike from inspecting plumbing or collecting fees for it inside a municipal corporation the Board of Building Standards has certified to enforce plumbing there. A separate clause excuses the division alone where a health district has given written notice and either employs certified plumbing inspectors or has contracted the work out.

So a health district inspects plumbing because it opted in and told the state, not because the chapter hands it the job. Which is why the honest answer to who inspects a bathroom is a question about the address, and why the table below names only the office each jurisdiction's own page names.

A mailing address is not a jurisdiction, and in Central Ohio that gap is wide. Delaware County's own routing sheet is the clearest case: the residential building permit comes from the county Department of Building Safety or from a city department in Delaware, Dublin, Powell, Westerville or Columbus, while the health office holds the plumbing side for the county, Powell included. Two offices, one project. That routing sheet calls the health office the Delaware General Health Department, while the office's own site calls itself the Delaware Public Health District; the two names reach the same office. Nothing here states a requirement for one particular address; the office named on yours does that.

What Ohio requires in the contract

One more chapter belongs here, because it is the one most often described wrongly. Ohio Revised Code chapter 4722 governs home construction service. Above a threshold the statute names, section 4722.02 says a supplier may not proceed "unless the supplier enters into a written home construction services contract with the owner," and lists nine items that contract must contain, one of them a certificate of general liability insurance. It creates no registry and issues no credential, and the word register does not appear in that section, so the widely repeated claim that Ohio residential contractors must register with the state under this chapter does not survive reading it. Taken with chapter 4740, whose contractor types are defined around projects that exclude residential buildings, the state's statutes contain no statewide home improvement license for a residential remodeler. That is an inference from two chapters rather than a quotation from either, and it is a statement about the state of Ohio and not about any company.

What a homeowner can do with this

Two questions settle most of it, both asked of a bidder rather than a code book. The first is who is doing the plumbing, because a license under chapter 4740 belongs to a named individual assigned to one contracting company. The second is which office will review and inspect the work, because that is set by the address. The permit page covers how the Columbus process reads from a homeowner's side, and the bids page covers how to read a written proposal. A house outside a public sewer or water system answers to a different set of offices, named on the wells and septic page, and what is in the walls is on the supply pipes page.

Sources

Every figure, date and quotation on this page comes from one of these documents, read on the date given. Where two of them disagree, the page says so.

• Ohio Board of Building Standards (Ohio Administrative Code), OAC 4101:8-1-01 Administration, Residential Code of Ohio, July 1, 2019; read September 2026.
• Ohio Board of Building Standards (Ohio Administrative Code), OAC 4101:8-25-01 Plumbing systems, Residential Code of Ohio, July 1, 2019; read September 2026.
• Franklin County Public Health, Plumbing and Medical Gas, undated; read September 2026.
• Ohio Board of Building Standards (Ohio Administrative Code), OAC Division 4101:8, Residential Code of Ohio chapter index and posted effective dates, undated; read September 2026.
• Ohio Board of Building Standards (Ohio Administrative Code), OAC 4101:3-1-01 Administration, Ohio Plumbing Code, October 15, 2025; read September 2026.
• Ohio Department of Commerce, Board of Building Standards, 2024 Ohio Plumbing Code Rules Effective March 1, 2024, August 2023; read September 2026.
• Ohio Board of Building Standards (Ohio Administrative Code), OAC 4101:3-4-01 Fixtures, faucets and fixture fittings, Ohio Plumbing Code, October 15, 2025; read September 2026.
• Ohio Laws (Ohio Legislative Service Commission), Ohio Revised Code Section 3781.10, Board of building standards, powers and duties, undated; read September 2026.
• UpCodes (Ohio Plumbing Code 2024), Chapter 4, Fixtures, Faucets and Fixture Fittings, Ohio Plumbing Code 2024, undated; read September 2026.
• Ohio Board of Building Standards (Ohio Administrative Code), OAC 4101:8-3-01 Building planning, Residential Code of Ohio, July 1, 2019; read September 2026.
• Ohio Laws (Ohio Legislative Service Commission), Ohio Revised Code Section 4740.02, Ohio construction industry licensing board, September 17, 2014; read September 2026.
• Ohio Laws (Ohio Legislative Service Commission), Ohio Revised Code Section 4740.01, Construction industry licensing board definitions, September 17, 2014; read September 2026.
• Ohio Department of Commerce, About the Ohio Construction Industry Licensing Board, undated; read September 2026.
• Ohio Laws (Ohio Legislative Service Commission), Ohio Revised Code Section 4740.06, License application, September 30, 2025; read September 2026.
• Ohio Laws (Ohio Legislative Service Commission), Ohio Revised Code Section 4740.07, Licenses issued to individuals, September 17, 2014; read September 2026.
• Ohio Laws (Ohio Legislative Service Commission), Ohio Revised Code Section 3781.06, Buildings to be safe and sanitary, definitions, undated; read September 2026.
• City of Columbus, Department of Building and Zoning Services, Contractor Licenses, undated; read September 2026.
• Ohio Laws (Ohio Legislative Service Commission), Ohio Revised Code Section 4740.12, Local regulation, regulation by other state agencies, March 30, 2007; read September 2026.
• Ohio Laws (Ohio Legislative Service Commission), Ohio Revised Code Section 3703.01, Division of industrial compliance, powers and duties, September 30, 2021; read September 2026.
• City of Columbus, Department of Building and Zoning Services, Plumbing, Building Inspections, undated; read September 2026.
• Franklin County Public Health, Inspectors by Area, Plumbing Program, revised February 5, 2026; read September 2026.
• Delaware Public Health District, Plumbing, undated; read September 2026.
• Delaware County Department of Building Safety, Permitting in Delaware County, June 5, 2025; read September 2026.
• Licking County Health Department, Environmental Health, undated; read September 2026.
• Fairfield County Health Department, Plumbing Program, undated; read September 2026.
• Fairfield County, Ohio, Building Department, undated; read September 2026.
• Ohio Laws (Ohio Legislative Service Commission), Ohio Revised Code Section 4722.02, Service contract, undated; read September 2026.

Common questions