NGWA CPI common mistakes
NGWA CPI · Understand the traps and how to avoid them.
Choosing a pump by horsepower alone and skipping the system-head calculation (static lift + drawdown + friction loss + pressure head) before matching the pump curve.
Horsepower feels like a simple proxy for capacity, and candidates who have only seen catalog marketing material assume a bigger motor always delivers more flow at the required pressure. They then miss operating-point questions where a high-head pump is required but a high-flow pump is the tempting distractor.
What to do instead
Practice building a head budget for at least five scenarios: total dynamic head = static water level + drawdown + vertical lift to discharge + friction loss in drop pipe, fittings, and discharge line + required discharge pressure converted to feet (psi x 2.31). Then plot that head on a pump curve and read the flow at the intersection. Always state the operating point explicitly before selecting a pump.
Confusing the pump's setting depth with the well's pumping water level, and installing the pump intake too close to the well bottom or too near the drawdown level.
Candidates memorize 'set the pump below the water level' without distinguishing static level, pumping level, and well depth. They forget that drawdown during operation lowers the water surface, and that a submersible intake set too deep can pull sand and sediment while one set too shallow can break suction or run dry.
What to do instead
For each problem, write the three numbers separately: static water level, expected pumping level at design flow, and total well depth. Set the pump intake at least the manufacturer's minimum submergence below the pumping level (commonly 10 ft or more, but use the stated figure), and keep it well above the well bottom or screen. Recheck the setting after any change in design flow.
Treating well yield, specific capacity, and drawdown as interchangeable, and predicting long-term yield from a short pump test without accounting for stabilized drawdown.
These terms appear together in test data, and candidates skim the definitions. A short-duration test reflects transient conditions, so extrapolating it overstates sustainable yield, which leads to wrong answers on safe-yield and pump-sizing questions.
What to do instead
Learn the definitions cold: specific capacity = pumping rate divided by drawdown, in gpm per foot. Practice computing it from a test table, then use it to estimate drawdown at a different rate. Always ask whether the drawdown reported is stabilized; if the test was brief, treat the yield figure as provisional and note the need for a longer test.
Mixing up the well construction and grouting requirements: casing depth, annular seal placement, and the purpose of the sanitary seal, and applying a rule from one well type to another.
Requirements differ by well type (domestic, public, monitoring, dewatering) and by state, and candidates memorize a single number such as a grout depth instead of the principle behind it. They also confuse the sanitary seal at the surface with the annular seal around the casing.
What to do instead
Study the function of each element first: the casing holds the borehole open and excludes shallow contamination, the annular seal prevents surface water from migrating down the outside of the casing, and the sanitary seal closes the top of the well against entry. Then attach the numeric minimums to each function and label which well type and which jurisdiction they belong to.
Sizing conductors, overload protection, and disconnect means from the motor's nameplate horsepower without using the motor service factor, ambient temperature, and the applicable table values.
Candidates reach for a familiar ampacity number or a rule of thumb from residential work and skip the table lookup. Pump motors run continuously in hot wellheads, and service-factor amps can exceed nameplate amps, so undersized conductors and heaters are a common wrong answer.
What to do instead
Work the problem in a fixed sequence: nameplate voltage, phase, and full-load amps; apply the service factor where the code or manufacturer allows; correct for ambient temperature and conduit fill; then select the conductor and the overload heater from the appropriate table. Show each step on scratch paper so an arithmetic slip is visible rather than buried.
Ignoring the difference between overload protection and short-circuit/ground-fault protection, and placing the wrong device at the wrong point in a submersible pump circuit.
Both are 'breakers' to a candidate without field experience. They then answer that a standard circuit breaker protects the motor from overload, or they omit the magnetic starter's overload heaters entirely, missing questions about nuisance tripping and burned windings.
What to do instead
Draw the circuit once, from the service panel through the disconnect, controller, and overload device to the motor. Label each device with what it protects against: short circuit, ground fault, overload, or undervoltage. Practice identifying which device trips on a locked rotor versus a gradual current rise, and remember that submersible motors often need overload protection sized for the motor, not the branch circuit.
Skipping the electrical safety steps before servicing a pump: not verifying lockout/tagout, not confirming zero energy at the controller, and not checking for a backfeed from a generator or a second supply.
Candidates read the question as a troubleshooting puzzle and jump to the diagnosis, forgetting that the scenario is a safety question. They also assume opening the disconnect removes all voltage, which is false where capacitors, VFDs, or alternate sources are present.
What to do instead
Treat every service scenario as a lockout/tagout question first: isolate, lock, tag, and verify with a meter at the point of work. Note stored energy in capacitors and VFD DC buses and allow discharge time. If a generator or transfer switch appears in the stem, state explicitly that the alternate source must be isolated too.
Answering regulatory questions from general memory instead of identifying the governing authority, the notification requirement, and the recordkeeping obligation for the specific activity.
Well construction, pump installation, and electrical work each fall under different authorities, and candidates blur them. They answer with a plausible practice rather than the required procedure, and they omit the paperwork step that the exam treats as part of the job.
What to do instead
For each regulated activity, build a three-part note: who must be notified before work, what must be submitted or reported after work, and who may legally perform it. Practice classifying scenarios by activity type and jurisdiction, and when a question gives a state or local rule, answer from that rule rather than from a general default.
Overlooking the business-practice side of a job: no written contract or change order, no lien notice or preliminary notice where required, and no documentation of the as-built condition.
Candidates focus on the technical domains and treat contract and lien questions as filler. In practice, disputes over scope changes and unpaid work are the most common business failure, and the exam tests whether the candidate knows that documentation protects the contractor.
What to do instead
Memorize the sequence for a typical job: written proposal and acceptance, notice of any lien rights or preliminary notice where the jurisdiction requires it, signed change orders before extra work, and a completion document with the as-built well log and pump data. Practice spotting the missing document in a scenario rather than only the missing part.
Diagnosing a pump problem from a single symptom without checking the whole system: calling a no-flow condition a failed pump when the cause is a dropped water level, a closed valve, a tripped overload, or a worn impeller.
Candidates memorize symptom-to-part mappings, so 'no water' maps to 'replace pump.' They skip the sequence of checks that separates an electrical fault from a hydraulic or mechanical one, and they miss questions that reward a systematic diagnosis.
What to do instead
Use a fixed troubleshooting order and apply it to every scenario: confirm power at the controller, check the overload and control settings, verify the water level and suction conditions, check valves and discharge pressure, then evaluate the pump itself. State which check rules out which cause. Practice writing the differential diagnosis for no flow, low flow, and cycling before choosing an answer.