Exam L is a closed-book, 50-question test with a one-hour limit and a 70 percent passing score, administered year-round at PSI test centers. Its questions concentrate on determining system component requirements (19) and troubleshooting existing pump systems (18). Passing it alone does not certify you: the CPI designation requires the Water Systems General exam plus your specialty exam within one 12-month period, along with experience, references, and application materials. Build preparation around the two heavy task areas using NGWA's recommended water systems texts, and confirm anything the sources leave open — such as the exact 100 GPM boundary — directly with NGWA.
What Exam L is and how it fits the CPI credential
Exam L, Water Systems Greater Than 100 GPM, is a specialty exam option for NGWA's Certified Pump Installer (CPI) designation, not a standalone credential.
The National Ground Water Association (NGWA) runs a voluntary certification program for groundwater contractors that started in 1970. NGWA describes it as the only national certification program for contractors and pump installers in the industry, governed by working contractors. To earn the CPI designation, you must pass the Water Systems General exam plus at least one specialized pump/water systems exam, both within a single 12-month period with scores of 70 percent or better.
Exam L is the specialty option for larger systems. The NGWA exam list places it in the pump categories as "Water systems more than 100 gpm," alongside Exam K for systems less than 100 GPM; the PSI candidate bulletin titles it "Water Systems Greater Than 100 GPM." It is one half of the CPI testing requirement, not a separate master credential.
Keep certification and licensing distinct in your planning. Many state agencies use these same exams within their own licensing programs, but NGWA certification itself is voluntary and does not replace a state license. Your state's rules control what you need to work legally there.
Sources checked: Groundwater | NGWA Certification exams — Certification Exams page: exam categories, preparation materials, fees, and PSI scheduling; Groundwater | NGWA Certification for contractors — Program overview and eligibility requirements; PSI NGWA candidate information bulletin — Cover September 20, 2022; content pages 5–7 marked May 2022; exam content tables
Exam format, scoring, and scheduling
Exam L is a closed-book, 50-question test with a one-hour time limit; you need 70 percent to pass, and you can sit it year-round at PSI test centers without prior NGWA approval.
The PSI candidate bulletin states that all NGWA examinations are closed book, so plan to work from memory. It also confirms that no NGWA approval is needed to sit an exam; certification application and eligibility are handled separately from test registration.
Exam L follows the standard contractor-exam pattern: 50 questions, a minimum passing score of 70 percent, and one hour allowed. The bulletin's content table lists these figures directly for Exam L, and NGWA's exam page confirms the ordinary 50-question, one-hour format.
PSI Services administers the exams online at more than 400 test centers nationwide, available year-round. Scheduling runs through PSI's website or phone line, and NGWA notes the process requires no special computer skills. If scheduling problems come up, NGWA asks candidates to email its certification office so it can work with PSI.
Scores print immediately after you finish, so collect your score report at the test center before leaving. NGWA can reissue a lost report for a fee, but scores are never given over the phone. All centers are ADA compliant, and candidates who need accommodations contact NGWA first, which forwards approval to PSI for registration.
One dating note: these logistics come from NGWA's current certification pages and the PSI bulletin dated 2022. Policies can change independently of technical content, so confirm current details with NGWA or PSI before you book.
Sources checked: Groundwater | NGWA Certification exams — Certification Exams page: exam categories, preparation materials, fees, and PSI scheduling; PSI NGWA candidate information bulletin — Cover September 20, 2022; content pages 5–7 marked May 2022; exam content tables
Content outline: what Exam L tests
Two task areas dominate Exam L: determining system component requirements (19 questions) and troubleshooting existing pump systems (18 questions), which together make up 37 of the 50 questions.
The bulletin's content table gives the full breakdown below. The remaining questions are spread thinly across site assessment, installation preparation, and installation, so component selection and diagnostics deserve most of your study time.
These areas mirror the daily duties in NGWA's DACUM job-task chart for pump installers: assessing customer needs and job sites, determining system component requirements, preparing and installing the pump system, and troubleshooting. NGWA publishes these charts specifically to help professionals studying for contractor certification. Note that the chart's duty letters (A through G) are just task-group labels and do not correspond to exam letters.
The Water Systems General exam, which you also need for the CPI, has its own outline weighted toward installing pump systems (16 questions) and troubleshooting (8). NGWA University's self-paced online courses target the general exams, while the study texts listed later cover material for all water systems exams.
| Testing area | Questions |
|---|---|
| Assess job site | 1 |
| Determine system component requirements | 19 |
| Prepare to install pump system | 1 |
| Install pump system | 11 |
| Troubleshoot existing pump system | 18 |
Sources checked: PSI NGWA candidate information bulletin — Cover September 20, 2022; content pages 5–7 marked May 2022; exam content tables; Pump installers (NGWA DACUM Research Chart) — Duties and tasks for pump installers; Groundwater | NGWA Certification exams — Certification Exams page: exam categories, preparation materials, fees, and PSI scheduling
Certification requirements beyond the exam
Passing Exam L is one piece of the CPI credential; you also need the Water Systems General exam, qualifying experience, references, and completed application materials within the deadline.
You must pass both the Water Systems General exam and your chosen specialty exam within one 12-month period, scoring 70 percent or better on each. Plan your two test dates with that window in mind rather than treating them as independent bookings.
Eligibility to apply adds experience requirements: you must be at least 20 years old and have at least 24 consecutive months of full-time drilling or pump installation experience. You also submit written experience references from two professional contacts who are not affiliated with your current company, plus an agreement form and an affidavit for the current year.
Application materials must be received within 12 months of the qualifying exam session. This paperwork deadline is separate from the requirement to pass both exams within one 12-month period. Gather the references and forms alongside your preparation.
Sources checked: Groundwater | NGWA Certification exams — Certification Exams page: exam categories, preparation materials, fees, and PSI scheduling; Groundwater | NGWA Certification for contractors — Program overview and eligibility requirements
How to prepare
Weight your study toward component requirements and troubleshooting, and use NGWA's recommended water systems texts and the pump installer task chart as your core materials.
NGWA recommends a specific set of texts for all water systems exams: the Professional Designations Information and Study Guide, Groundwater & Wells (third edition), the Water Systems Handbook (13th edition), Engineering Your Business, and Basic Water Systems: A Pump and Hydraulic Training Manual. The study guide can be purchased through the NGWA online store, and NGWA customer service can direct you to the other materials.
NGWA University offers self-paced online training for the general drilling and water systems exams, developed by NGWA-approved subject matter experts with Oklahoma State University education specialists. The courses include knowledge checks, study guides, and video lectures, which suits candidates who prefer structured review before the specialized exam.
- Prioritize component requirements and troubleshooting — together they carry 37 of Exam L's 50 questions.
- Read the DACUM pump installer chart and connect each exam area to a real field duty, from assessing the job site through troubleshooting and administrative follow-up.
- When practice material reports a drawdown, capacity, or yield figure, check the pumping rate it was measured at before reusing the number at a different condition.
- Verify current fees, policies, and scheduling details on the NGWA certification pages or with PSI before booking.
Sources checked: Groundwater | NGWA Certification exams — Certification Exams page: exam categories, preparation materials, fees, and PSI scheduling; PSI NGWA candidate information bulletin — Cover September 20, 2022; content pages 5–7 marked May 2022; exam content tables; Pump installers (NGWA DACUM Research Chart) — Duties and tasks for pump installers; USGS Basic Ground-Water Hydrology (Water-Supply Paper 2220, 1983) — Selected fundamentals: well development and specific capacity definition
Worked practice: compare two specific-capacity readings
Specific capacity is pumping rate divided by drawdown measured at the same time. Calculate each supplied pair separately; the ratios alone do not predict an untested operating condition.
The pump task chart includes evaluating well test results and water-source parameters. This original exercise uses the USGS definition to describe two observations, without choosing a pump or extrapolating a design drawdown.
Practice problem
In one test, the pumping rate is 300 gpm and the drawdown measured at the same time is 25 ft. In a second test, the paired readings are 150 gpm and 10 ft. Calculate specific capacity for each pair. Do these two ratios, by themselves, establish drawdown at an untested rate of 250 gpm?
Show answer
The first ratio is 300/25 = 12 gpm/ft. The second is 150/10 = 15 gpm/ft. These observations alone do not establish drawdown at 250 gpm.
Each division uses rate and drawdown from the same test moment. The supplied data give different ratios. Treating either ratio as constant at another rate adds an assumption that the problem does not establish. The calculation describes the observations; it does not select a pump or prove sustainable yield.
Sources checked: USGS Basic Ground-Water Hydrology (Water-Supply Paper 2220, 1983) — Selected fundamentals: well development and specific capacity definition; Pump installers (NGWA DACUM Research Chart) — Duties and tasks for pump installers
Sources checked
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