Sanitation system contractor installing a septic tank and leach field

Become a Licensed C-42 Sanitation System Contractor

The C-42 Sanitation System classification covers the structures that handle waste and drainage, septic tanks, cesspools, storm drains, and the sewage-disposal systems that serve properties off the municipal grid.

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Requirements

Minimum age: 18+ is CSLB's normal applicant path. A minor may qualify only after a court appoints a guardian (BPC §7065.5)
Experience required: 4 full-time-equivalent years of journey-level experience within the past 10 years; CSLB prorates part-time work
Contractor bond: $25,000

About the Exam

Exam format: 2 parts (Law & Business + Trade)
Law & Business exam: 115 questions
School-observed scores: 65% Law / 65% Trade; not published as fixed by CSLB
Application fee: $450

License renews every 2 years. Governing code: CCR §832.42

About this classification

What does a C-42 Sanitation System contractor do?

A C-42 Sanitation System Contractor fabricates and installs cesspools, septic tanks, storm drains, and other sewage-disposal and drain structures, using cast-iron, steel, concrete, vitreous, and nonvitreous pipe. It is the specialty for building on-site waste-disposal and drainage systems.

Under the California Code of Regulations (Title 16, §832.42), a C-42 contractor "fabricates and installs cesspools, septic tanks, storm drains, and other sewage disposal and drain structures." The classification focuses on the disposal and drainage structures themselves rather than the plumbing inside a building.

Official source: CSLB C-42 classification · CSLB fee schedule Last reviewed: March 2026

Scope of work

Septic tanks and leach fields
Cesspools and aerobic treatment units (ATUs)
Storm-drain collection systems
Sewer laterals and cleanouts
French drains and subsurface drainage
Greywater reuse systems
Drain structures in cast iron, concrete, and vitreous pipe
On-site sewage-disposal systems

Important notes

The C-42 builds disposal and drainage structures, the supply and waste plumbing inside a building is the C-36 (Plumbing) classification.
Municipal sewage-treatment plants and large fixed-works sanitation infrastructure fall under the A (General Engineering) license.
A C-42 installs terminal disposal structures; the conveyance pipeline that carries fluids over distance is the C-34 (Pipeline) scope.
California requires a license for any sanitation contract over $1,000 (labor and materials combined), and workers' compensation coverage is required once you have employees; sole owners with no employees may file an exemption (BPC §7125(b)).

The CSLB exam

What's on the C-42 Sanitation System exam?

California requires you to pass a two-part CSLB exam: the Law & Business exam (the same for every classification) and the C-42 Sanitation System trade exam. CSLS has observed scores of 65% for Law & Business and 65% for the C-42 trade exam. CSLB does not publish fixed passing scores and may vary them by exam version.

Law & Business

Same for all classifications

115 questions, multiple choice, computer-based
3.5 hours allotted
Topics: California contractor law, business management, safety, estimating, project management

C-42 Trade Exam

Sanitation System-specific

about 100 questions, multiple choice, computer-based
3.5 hours allotted
Topics: septic-system design, leach-field sizing, soil percolation, drain piping and materials, storm-drainage, excavation and backfill, health-code requirements, plan reading

How to Get Your C-42 Sanitation System License

Step 1

Qualify

18+ is CSLB's normal applicant path. A minor may qualify only after a court appoints a guardian (BPC §7065.5). You also need a valid SSN/ITIN and 4 full-time-equivalent years of journey-level sanitation system installation experience within the past 10 years; CSLB prorates part-time work. Up to 3 years may be substituted with approved education or apprenticeship.

Step 2

Apply to CSLB

Submit your application, get fingerprinted, and pay the $450 application fee. Processing times vary; check the CSLB's current processing times.

Step 3

Study & Prepare

Prepare for both exam parts, on your own or with a CSLS exam prep program. 99% of CSLS students pass on their first try, backed by our 100% Money-Back Guarantee.

Compare programs

Step 4

Pass the Exam

Two parts: Law & Business (115q, 3.5 hrs) + C-42 Trade. Multiple choice, computer-based. CSLS has observed scores of 65% Law & Business / 65% C-42 Trade; CSLB does not publish fixed passing scores and may vary them by exam version.

Step 5

Get Licensed

Post your $25,000 contractor bond, pay the $200 license fee, and receive your C-42 license. You're officially in business.

Step 1

Qualify

Step 2

Apply to CSLB

Submit your application, get fingerprinted, and pay the $450 application fee. Processing times vary; check the CSLB's current processing times.

Step 3

Study & Prepare

Prepare for both exam parts, on your own or with a CSLS exam prep program. 99% of CSLS students pass on their first try, backed by our 100% Money-Back Guarantee.

Compare programs

Step 4

Pass the Exam

Step 5

Get Licensed

Post your $25,000 contractor bond, pay the $200 license fee, and receive your C-42 license. You're officially in business.

Exam Prep Programs

Compare C-42 Sanitation System Exam Prep Programs

Every program prepares you for the required CSLB exam for C-42 Sanitation System. Our 99% first-time pass rate is backed by the 100% Money-Back Guarantee on eligible programs.

Feature-by-feature comparison of all four CSLS exam prep programs
Features	Most Popular All-Inclusive C-42 Sanitation System $1,195.00 Value: $2,500	Live Online C-42 Sanitation System $695.00 Value: $995	Crash Course C-42 Sanitation System $495.00 Value: $695	Home Study C-42 Sanitation System $295.00 Value: $395
Best For	Comprehensive prep with maximum support	Remote learners wanting live instruction	Experienced pros with an exam date soon	Self-directed independent learners
Law & Business Classes	4 Classes + Full-Day Review	4 Live Online + Review	Full-Day Review Only	Not included
Trade Math Training	30-Day Interactive + Review	Online Video Review	14-Day Crash Course	Not included
Test-Taking Skills Seminar	1-Day In-Person	1-Day Online	Not included	Not included
Law & Business Materials	Online; binder add-on available	Online; binder add-on available	Online; binder add-on available	Online; binder add-on available
Trade-Specific Materials	Online; binder add-on available	Online; binder add-on available	Online; binder add-on available	Online; binder add-on available
Study Materials	Full Online Suite	Online Materials + Audio/Video	Online + Audio/Video	Online + Audio
Online Videos	Full Suite: L&B, Trade, H&S, Math	Audio + H&S + Math Videos	Audio + H&S + Math Videos	L&B Audio + H&S Video
Law & Business Practice Exams	6 Months	2 Months	30 Days	30 Days
Trade Practice Exams	6 Months	2 Months	30 Days	30 Days
School Location Access	25+ Locations	25+ Locations	25+ Locations	Self-Study Only
Application Assistance	Preparation & Review	Review Only	Review Only	Not included
Money-Back Guarantee	Included	Included	Included	Not included
Bond Fee Discount	50% off first-year bond, up to $120	Not included	Not included	Not included
Retail Value	$2,500	$995	$695	$395
Choose a program	Get All-Inclusive	Get Live Online	Get Crash Course	Get Home Study

Not sure which fits? Call 800-809-6463. Prices and inclusions are subject to change.

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Common Questions

C-42 Sanitation System license FAQ

The C-42 (Sanitation System) builds the disposal and drainage structures, septic tanks, leach fields, cesspools, and storm drains. The C-36 (Plumbing) handles the supply and waste plumbing inside the building. The C-42 builds the system that receives the waste; the C-36 connects the building to it.

Yes. Septic tanks, leach fields, cesspools, and aerobic treatment units are core C-42 scope. The classification specifically covers fabricating and installing sewage-disposal and drain structures, which is exactly what an on-site septic system is.

The C-42 installs terminal disposal and drain structures, septic tanks, storm drains, cesspools. The C-34 (Pipeline) installs conveyance pipelines that carry water, gas, or petroleum over distance. The C-42 is about where the fluid ends up and is treated; the C-34 is about moving it from one place to another.

Most students are exam-ready in 4–6 weeks of CSLS prep. Adding CSLB application processing (typically 2–4 weeks), exam scheduling, and posting your $25,000 bond, the full path usually runs 2–4 months from start to license-in-hand.

4 full-time-equivalent years of journey-level sanitation system installation experience within the past 10 years; CSLB prorates part-time work. Qualifying work may be as a journeyperson, foreperson, supervising employee, contractor, or owner-builder. This can include work as a journeyman, foreman, or supervising employee. Up to three years can be satisfied with approved technical training, apprenticeship, or education.

The C-42 trade exam covers septic-system design, leach-field sizing, soil percolation, drain piping, and storm-drainage. You need the current version-specific CSLB passing score to pass. With CSLS exam prep, 99% of students pass on their first attempt, backed by our 100% Money-Back Guarantee.

Plan on roughly $885 in mandatory costs before exam prep: the $450 application fee, the $200 initial license issuance fee, about $150 for the first-year premium on your $25,000 bond, and around $85 for fingerprinting. Exam prep is separate.

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Become a Licensed C-42 Sanitation System Contractor

What does a C-42 Sanitation System contractor do?

Scope of work

Important notes

What's on the C-42 Sanitation System exam?

Law & Business

C-42 Trade Exam

How to Get Your C-42 Sanitation System License

Qualify

Apply to CSLB

Study & Prepare

Pass the Exam

Get Licensed

Qualify

Apply to CSLB

Study & Prepare

Pass the Exam

Get Licensed

Compare C-42 Sanitation System Exam Prep Programs

Labor Day Promo 2026

What our Sanitation System students say

Try a free C-42 Sanitation System practice exam

C-42 Sanitation System license FAQ

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