A-12 is the Arizona Registrar of Contractors commercial class for Sewers, Drains and Pipe Laying. Rule R4-9-102 lets the holder install and repair sewer access holes and pipe for storm drains, water and gas lines, irrigation and sewers, plus septic tanks, leach lines, dry wells, and the related excavating and backfilling.
What the A-12 rule actually says
The scope is set by Arizona Administrative Code R4-9-102, the Registrar's list of commercial classifications. It files A-12 under "ENGINEERING CONTRACTING," next to classes like A-4 Drilling and A-16 Waterworks.
The rule says the A-12 classification "allows the licensee to install and repair any project involving sewer access holes, the laying of pipe for storm drains, water and gas lines, irrigation, and sewers." It goes on: "Includes connecting sewer collector lines to building drains and the installation of septic tanks, leach lines, dry wells, all necessary connections, liners and related excavating and backfilling."
Put that into job terms and you get a list like this:
- Sewer laterals and the tie-in between a building drain and the sewer collector line
- Storm drain pipe, such as the line from a parking lot catch basin to a retention basin
- Dry wells, the bored stormwater wells that drain many Valley retention basins
- Septic tanks and leach lines
- Underground water, gas and irrigation pipe
- Sewer access holes (manholes)
- The trenching, excavating and backfill each of those jobs needs
How A-12 differs from a C-37 plumbing license
The short version: C-37 is building plumbing, A-12 is pipe in the ground. The full breakdown of C-37, R-37 and CR-37 is on our page about Arizona plumbing license classes, so this is only the comparison.
The C-37 rule covers fixtures, appliances, water supply piping, drain and vent systems, gas piping and water heating inside the property. It also says that work is "performed solely within property lines and not on public easements or right-of-ways, except as hereinafter provided." The exception lets sewer, gas and water service lines run from the structure to the nearest point of public supply or disposal, with limits on size and routing in public ground.
The A-12 text reads differently in two ways. It doesn't list fixtures, appliances or water heaters at all. And it has no property-line clause written into it. So a toilet, a water heater or a repipe is plumbing work. A storm drain, a long sewer run or a drywell is A-12 work. Septic tanks and leach lines show up in both rules, so either class can cover those.
| Class | Family | What the rule covers, in short |
|---|---|---|
| A-12 Sewers, Drains and Pipe Laying | Commercial engineering | Sewers, access holes, storm drain pipe, water, gas and irrigation lines, septic tanks, leach lines, dry wells, related digging |
| C-37 Plumbing | Commercial specialty | All plumbing within property lines, with the service-line exception |
| A-4 Drilling | Commercial engineering | Drilling and boring, wells, and "constructing dry wells, and monitor wells" |
| A General Engineering | Commercial engineering | Large fixed works, and "the scopes of work allowed by the A-4 through A-19" |
| CR-80 Sewers, Drains and Pipe Laying | Dual | The A-12 scope plus the residential R-37R sewers scope |
Where A-12 sits next to other classes
A-12 isn't the only class that touches this work. Rule R4-9-102 also gives A-4 Drilling the job of "constructing dry wells," so a drywell can involve a drilling contractor for the bore and an A-12 contractor for the pipe and connections. A-5 Excavating, Grading and Oil Surfacing covers digging and trenching, but that rule says it "does not allow the licensee to excavate for water, gas or oil wells." And the A General Engineering class includes the A-4 through A-19 scopes, so a general engineering contractor can cover A-12 work too.
On the residential side, R4-9-103 lists an R-37R Sewers, Drains and Pipe Laying subclass. The same rule says no new applications for that subclass are accepted, so you'll mostly see it on older licenses. The dual rule, R4-9-104, has CR-80, which "allows the scopes of work permitted by the commercial A-12 Sewers, Drains, and Pipe Laying and the residential R-37R Sewers, Drains and Pipe Laying licenses."
Does a property owner need an A-12 to do this work?
Usually not for work on your own place, under narrow conditions. A.R.S. 32-1121(A)(5) exempts owners who do the work themselves or with their own employees, but only when the property is "intended for occupancy solely by the owner" and isn't meant for the public as "employees or business visitors," and isn't built for sale or rent. A shopping center, office or apartment complex doesn't fit that. For those, the person doing the work for pay needs the right class. Our page on licensed contractors versus handymen covers the small-job limit.
What to do before you hire for underground work
- 1Name the job. Sewer lateral, storm drain line, drywell, catch basin line or septic? That tells you which class to look for.
- 2Ask for the license number and every class on it. One company can hold several, such as C-37 and A-12.
- 3Check it yourself. Our guide to verifying a plumber's ROC license shows where to look and what to confirm.
- 4For a drywell, also ask about design and registration. See who can legally install or clean a drywell in Arizona.
HQ holds an Arizona A-12 license, and we service drywells, retention basins and catch basins under it. On a drywell we clean the sludge off the leach rock, and on a catch basin we jet the line all the way to the retention area. If you're not sure your job is A-12 work, ask us. Estimates are free.