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jobs you can do with a C-55 license in California

What Can I Do With a C-55 Contractor License?

Table of Contents


What Jobs Can You Bid with a C-55 License?

The C-55 license is for individuals or companies that specialize in water conditioning and filtration work.

There are a variety of jobs you can bid on if you have this license, including:

  • Water systems repair and installation
  • Residential & commercial systems
  • Filtration replacement services
  • Reverse osmosis
  • Bottled water delivery
  • In home test analysis
  • Nanofiltration systems
  • Installation of Alkaline water systems
  • Troubleshooting water softeners
  • Equipment inspection
  • Beverage filtration systems
  • FDA compliance consultations
  • Adjusting all bleed & feed control ranges
  • Ion exchange
  • Acid cleanings
  • Chemical services
  • Biological control
  • Private water well treatment
  • Salt free conditioners
  • Ultra violet (UV) systems
  • Membrane cleaning
  • Remote monitoring solutions
  • Chemilizer pumps
  • Filtration hybrids
  • Expedient system qualification
  • Analytical sampling
  • Whole house water conditioning systems
  • Validation delivery
  • Reporting
  • House water filtration systems
  • Industrial water systems design
  • Water specialties
  • Water conservation
  • Anti-scale water conditioning
  • Treatment specialists
  • Water treatment services

Water Conditioning Contractors and the CSLB

The C-55 license is one of 74 classifications available in California. Contractors in the state of California are governed by the CSLB(Contractors State License Board)

There are 4 major classification categories:


Common Pairings for the C-55 License

Contractors in California can hold multiple classifications.

The most common pairing for the C-55 license is



C-55 contractor requirements

To become licensed with the CSLB you must meet the following basic requirements:

  • 18 Years of Age
  • 4 Years of Journeyman Level Experience
  • Social Security or ITIN #
  • Not Currently on Probation or Parole
  • Signature from a licensed contractor, fellow employee, supervisor, or business associate 


What water filtration concepts do I need to know for the exam?

You will definitely want to be prepared for any curveballs that could come up on the California C-55 license exam.

You may be presented with questions related to reverse osmosis and plumbing that could be unfamiliar.

Take the time to review every possible question and concept.

Below is a breakdown of what you need to know:

Planning and Estimating (22%)

  • Water analysis
  • Job site evaluation
  • System selection
  • Planning and estimating

Water Systems, Component Installation, and
Startup (29%)

  • Piping and valves
  • Equipment installation
  • Drain connections/backflow
  • Electrical connections
  • Startup and calibration

Troubleshooting, Maintenance, Repair,
and/or Replacement (34%)

  • Service and maintenance
  • Troubleshooting
  • Repair and replacement
  • Disinfection

Safety (15%)

  • Personnel safety
  • Handling hazardous materials
  • Environmental safety
  • Tool and equipment safety


What’s the C-55 license exam process like?

The exam will be:

  • 115 Questions Law & Business
  • 115 Questions Water Conditioning
  • Multiple Choice
  • Closed Book
  • 3 Hours to Complete each section
  • Taken via Computer at a CSLB Testing Facility
  • Exam Centers in: Berkeley, Fresno, Norwalk, Oxnard, Sacramento, San Bernardino, San Diego, and San Jose

Math Skills 

There will be math on your CSLB law & business and trade exam.

On the law side, questions will be presented to you as if you are a General Contractor with multiple projects running simultaneously with several employees.

You can expect math questions related to:

  • Arithmetic
  • Cost Estimation 
  • Percentages and Decimals

The math you can expect on the C-55 license exam may vary. Be prepared for questions that may include:

  • Basic Geometry
  • Units of measurement

Blueprint Reading Skills

Blueprint reading is a fundamental skill for all contractors.

Knowing how to interpret plans is a key part of the job if you are working within a construction crew.

Interpreting building plans is critical.

Some aspects of plan reading may also be your examination. 

For a deeper look at blueprint reading concepts, you will want to check out this free blueprint reading guide.


CSLB law & business exam

Our complete course gives you everything you need to pass the C-55 California water conditioning contractor license exam.

In addition to getting brushed up on the construction trade, those looking to get the C-55 license will be equipped with a crash course on how to run a profitable business. 

You will learn:

  • Company organization 
  • How to bid effectively
  • Understanding cost control
  • Various contract types
  • Cash management
  • Estimation fundamentals
  • CAL/OSHA
  • Business Structures
  • Worker’s Compensation and Taxes
  • Insurance Types in Construction
  • Labor Laws and Employee Rights
  • Hiring and Firing Practices
  • Contractor Bonds
  • Mechanics Liens
  • State Laws and Statutes
  • Project Management 101
  • Prevailing Wages and Public Works
  • And Much More!