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Certified Installer of Onsite Wastewater Treatment Systems (CIOWTS) Credential 


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Exam and Application

Exam Description and Content Outline

There are 75 questions on the basic level exam, and 125 questions on the advanced level exam. All questions are written in multiple choice format. You will have 2 hours to complete the basic level exam and 3 hours to complete the advanced level exam. The CIOWTS exam is based upon the following content areas. Next to each subject area the approximate percentage of questions in that content area on the exam. The content areas and approximate percentages of exam questions are the same for both the basic level and the advanced level. The advanced level exam includes more questions and questions of greater difficulty.



  • Knowledge of site plans; basic surveying; topography; site features

  • Knowledge of materials requirements; standards and specifications; soil profile descriptions; pump performance; treatment and dispersal technologies

  • Ability to conceptualize an installation activity

  • Ability to make mathematical calculations of area, volume, elevation, rates, measures and weights


  • Knowledge of installation plans; elevations; topography

  • Ability to transfer designerís plan to site; reconcile variations; identify conflicts

  • Knowledge of equipment needs and limitations; materials and supplies; soil characteristics

  • Ability to make mathematical calculations

  • Ability to identify subcontractor and homeowner needs and potential conflicts


  • Knowledge of soil characteristics; ability to recognize soil characteristics in the field

  • Knowledge of specifications and installation techniques for tanks, baffles, filters and screens, piping and fittings, aggregate and fill material, proprietary treatment components, pumps and siphons, liner materials, valves, switches and tubing

  • Knowledge of electrical requirements

  • Knowledge of gravity and pump/siphon dosed system requirements

  • Knowledge of timers and remote monitoring

  • Knowledge of bedding, testing, pipe connection methodologies

  • Knowledge of pump performance specifications; total dynamic head in pressurized systems

  • Ability to make mathematical calculations, conversions


Recommended Study References

Below is a list of study references that are recommended to assist the candidate in preparing for the CIOWTS examination.


1.   Installation of Wastewater Treatment Systems, CIDWT Ė available for purchase through NEHAís Bookstore.   *Recommended reference

2.   U.S. EPA Onsite Wastewater Treatment Systems Manual 

3.   Residential Building Design & Construction. Jack Willenbrock, Harvey Manbeck, and Michael Suchar, (1998) Prentice-Hall.

4.   Septic System Checkup: The Rhode Island Handbook for Inspection and Inspection Report Forms 

5.   Small and DeCentralized Wastewater Management Systems. Crites & Tchobanoglous. (1998) McGraw-Hill.

6.   Wells and Septic Systems, 2nd Edition. Max & Charlotte Alth, Revised by S. Blackwell Duncan, (1992) TAB Books.

7.   Plumberís Handbook Revised Edition. Howard Massey (1978).

8.   OSHA Guidelines

9.   Plumberís Guidelines

10. Glossary of Terms by CIDWT



Completing the Application

Applications must be completed and returned to NEHA for review at least 4 weeks prior to the exam date. If an application is received less than 4 weeks prior to when an examination is being given you may have to schedule the exam for another date.

A complete application should include:

  1. Completed NEHA Application.

  2. Copy of Drivers License to verify age.

  3. Work Experience Verification Form signed by a third party.

  4. Appropriate fees.


Exam Fees

All fees should accompany the NEHA Application.

CIOWTS-Basic Level

Fees Member Rate Non-Member Rate
Application fees $25.00  $50.00
Examination fees $125.00 $150.00

CIOWTS- Advance Level

Fees Member Rate Non-Member Rate
Application fees $50.00  $85.00
Examination fees $145.00 $170.00
Pearson VUE fee
(If applicable)
$100.00 $100.00


Exam Scheduling and Locations

Candidates can choose to schedule the CIOWTS examination in several different ways:

  1. The CIOWTS exam is offered annually at the NEHA Annual Educational Conference (AEC) & Exhibition.

  1. State Affiliate and Regional Meetings periodically offer the CIOWTS exam at their meetings/conferences. An up to date listing of these meeting/conference offerings can be found at the NEHA website

  1. Candidates can choose to take the exam on computer through Pearson VUE.  By choosing this option candidates can schedule the examination at their convenience at one of Pearson VUEís testing locations nationwide. To find a Pearson VUE testing center near you please visit Taking the exam at Pearson VUE not only offers the candidate flexibility in scheduling the exam, but also allows the candidate to receive his/her unofficial scores immediately following the conclusion of the exam.

  1. Special test sites may be arranged through NEHA in cooperation with the test vendor, PTI. In order to accommodate requests for special test sites, arrangements must be made a minimum of 6-8 weeks prior to the requested date. The fee to set up a special test site is $350.00. For groups of 10 or more candidates, the special test site fee is waived. Please complete the Special Test Site Request form (Appendix A) and return it to NEHA with your application.


Special Accommodations for Candidates with Disabilities or Impairments

NEHA is committed to ensuring that no individual is deprived of the opportunity to take a credentialing examination solely by reason of a disability or impairment. All test centers are fully accessible and compliant with the American with Disabilities Act (ADA).

To make a request for special accommodations you must complete the Accommodation Request Form and Documentation of Disability Related Needs Form including the specific diagnosis of your disability; medical records, or other written proof of the diagnosis by an appropriate licensed professional; and the type of accommodation being requested.  All form and documentation must be returned to NEHA at least 8 weeks prior to the scheduled test date. To receive a copy of the form please contact

If the forms are not returned to NEHA within 8 weeks prior to the scheduled test date your request for special accommodations may not be honored or may be delayed. 

With respect to all matters related to testing accommodations, NEHA will only communicate with the candidate, professionals knowledgeable about the candidateís disability or impairment, and the candidateís authorized representative (if applicable).

Admission to the Exam

NEHA will send an admission ticket approximately 2 weeks prior to your test date. The admission ticket will detail the exam date and location, reporting time, and starting time. Those that do not appear on the date of the exam at the appropriate time will forfeit all exam fees. Persons arriving after the examination has started may not be admitted.

If you lost your admission ticket or have not received an admission ticket at least 2 days prior to the test date, please contact NEHA immediately.

Only approved candidates will be admitted to the exam. No walk-in applicants will be admitted.

On test day please bring with you your admission ticket, photo identification (i.e. driverís license or passport), and sharpened #2 pencils.

FOR PEARSON VUE CANDIDATES: NEHA will send you an authorization letter via e-mail when your application is processed as approved. The letter will have your PTI ID number and the Pearson VUE website to schedule a testing time. 

On test day please bring your photo identification (i.e. driverís license or passport).



The passing score for the NEHA CIOWTS exam Levels A & B, is 70%. Your score will be based on the number of questions answered correctly. If you are unsure of the answer it is better to guess. You will not be given credit for any question left blank. 

Your exam results will be mailed to you from the NEHA office 4-6 weeks after the administration. To insure confidentiality, exam scores will not be released over the phone, via fax or email.



Credential Maintenance

Once you have obtained the CIOWTS credential you must maintain it. To keep your credential in good standing you must: 

1.    Earn a minimum of 12 hours of continuing education every two years; and

2.    Submit renewal fees for your credential every two years ($125.00 Basic level; $125.00 Advanced level).