Page 1 of 111
NGWA Water Systems General EXAM QUESTIONS AND
CORRECT VERIFIED SOLUTIONS LATEST UPDATE THIS YEAR –
JUST RELEASED
NGWA Water Systems General Exam
10-Line Exam Coverage in Points Form
1. Hydrogeology Fundamentals – Unconfined vs. confined aquifers (confined bounded by
impermeable layers), porosity (void space percentage), permeability (water transmission
ability), hydraulic conductivity (ease of water movement in distance/time units), and
specific yield (drainable water volume) .
2. Well Construction Standards – NGWA Code of Excellence requires minimum 18 ft casing
depth for sanitary seal; bentonite grout (minimum 20% solids) for annular sealing;
minimum 10 ft grout seal in confined aquifers .
3. Pump Systems & Hydraulics – Pump types include submersible, jet (shallow/deep well),
and line shaft turbine; Total Dynamic Head (TDH) = static lift + friction loss + pressure
head; 1 psi = 2.31 ft of head .
4. Pump Affinity Laws – Flow (Q) varies directly with speed (N); Head (H) varies with N²;
Power (P) varies with N³. A 10% speed increase yields ~10% more flow, ~21% more head,
and ~33% more power .
5. Pressure Tanks & Controls – Common pressure switch settings: 20/40, 30/50, 40/60 psi;
tank pre-charge set 2 psi below cut-in pressure; drawdown volume prevents short
cycling; waterlogged tank causes rapid cycling .
6. Well Development Methods – Surging (most effective for removing fines), air lift
pumping, overpumping, and bailing; development removes drilling fluids and increases
hydraulic conductivity; wells should produce <5 mg/L sand at design rate .
7. Water Quality Treatment – Aeration oxidizes iron and hydrogen sulfide; water softeners
use ion exchange; chlorination requires 30 minutes contact time with 50-200 mg/L
chlorine; reverse osmosis removes TDS .
8. Electrical & Safety – Lock-out/Tag-out required by OSHA 29 CFR 1910.147 when
servicing pumps; 1 HP = 746 watts; confined space entry requires atmospheric testing .
9. Pumping Tests – Step-discharge test: minimum 4 steps at 50-110% of design capacity;
constant-rate test: minimum 24 hours; recovery water levels recorded after pumping
stops .
10. Plumbness & Alignment – Casing >12 inches: maximum horizontal deviation ≤ ¾ ×
smallest casing ID per 100 ft; dummy test: 40-ft rigid apparatus, ½ inch smaller than
casing ID for ≤12-inch casing .
, Page 2 of 111
250 MCQs with Rationales
1. According to the NGWA Code of Excellence, what is the minimum depth to which casing
must be installed to provide a sanitary seal for a residential well?
A) 10 feet
B) 14 feet
C) 18 feet
D) 24 feet
Answer: C
Rationale: The NGWA Code of Excellence requires installing casing to at least an 18-foot depth
for sanitary sealing, followed by surface sealing and installation of a sanitary well cap to prevent
surface water and contaminant entry .
2. In the context of hydrogeology, what best describes the term "porosity"?
A) The ability of rock or soil to transmit water
B) The percentage of void space within a rock or soil that can hold water
C) The rate at which water moves through a material
D) The pressure exerted by water in an aquifer
Answer: B
Rationale: Porosity is the percentage of void spaces within a material, indicating how much
water it can potentially hold. It does not measure the ease of water movement—that is
permeability .
, Page 3 of 111
3. A well is drilled into a confined aquifer. What is the primary purpose of sealing the annular
space with grout?
A) To prevent loss of aquifer pressure only
B) To prevent vertical migration of contaminants into the confined aquifer
C) To prevent corrosion of the casing
D) To prevent entry of sand into the well
Answer: B
Rationale: Annular space grouting (minimum 10 ft in confined aquifers) seals off the annulus to
prevent water and contaminants from moving vertically between aquifers, protecting the
confined aquifer from surface contamination .
4. What property of water describes its resistance to flow and deformation, directly affecting
pump selection and energy requirements?
A) Density
B) Viscosity
C) Conductivity
D) Surface tension
Answer: B
Rationale: Viscosity measures a fluid's resistance to flow. Higher viscosity (e.g., cold water or
fluids with additives) creates more resistance, requiring more energy to pump, which directly
influences pump selection and system design .
, Page 4 of 111
5. What is the conversion factor for pressure (psi) to head (feet of water column) at sea level?
A) 1 psi = 1.00 ft of head
B) 1 psi = 2.31 ft of head
C) 1 psi = 4.33 ft of head
D) 1 psi = 7.00 ft of head
Answer: B
Rationale: At sea level, 1 psi equals 2.31 feet of water column. This conversion is fundamental
for calculating Total Dynamic Head and pump selection .
6. What grouting material is most commonly specified for well sealing to prevent
contamination?
A) Neat cement (Portland cement)
B) Bentonite clay (minimum 20% solids)
C) Bentonite-cement mixture
D) Sand and gravel
Answer: B
Rationale: Bentonite grout (20% solids minimum) is the preferred material for well sealing
because it swells upon hydration and provides a low-permeability seal. It is specified in NGWA
standards for annular space sealing .
7. In water systems, what does GPM stand for as a standard unit of measurement?
A) Gallons per meter
B) Gallons per minute
NGWA Water Systems General EXAM QUESTIONS AND
CORRECT VERIFIED SOLUTIONS LATEST UPDATE THIS YEAR –
JUST RELEASED
NGWA Water Systems General Exam
10-Line Exam Coverage in Points Form
1. Hydrogeology Fundamentals – Unconfined vs. confined aquifers (confined bounded by
impermeable layers), porosity (void space percentage), permeability (water transmission
ability), hydraulic conductivity (ease of water movement in distance/time units), and
specific yield (drainable water volume) .
2. Well Construction Standards – NGWA Code of Excellence requires minimum 18 ft casing
depth for sanitary seal; bentonite grout (minimum 20% solids) for annular sealing;
minimum 10 ft grout seal in confined aquifers .
3. Pump Systems & Hydraulics – Pump types include submersible, jet (shallow/deep well),
and line shaft turbine; Total Dynamic Head (TDH) = static lift + friction loss + pressure
head; 1 psi = 2.31 ft of head .
4. Pump Affinity Laws – Flow (Q) varies directly with speed (N); Head (H) varies with N²;
Power (P) varies with N³. A 10% speed increase yields ~10% more flow, ~21% more head,
and ~33% more power .
5. Pressure Tanks & Controls – Common pressure switch settings: 20/40, 30/50, 40/60 psi;
tank pre-charge set 2 psi below cut-in pressure; drawdown volume prevents short
cycling; waterlogged tank causes rapid cycling .
6. Well Development Methods – Surging (most effective for removing fines), air lift
pumping, overpumping, and bailing; development removes drilling fluids and increases
hydraulic conductivity; wells should produce <5 mg/L sand at design rate .
7. Water Quality Treatment – Aeration oxidizes iron and hydrogen sulfide; water softeners
use ion exchange; chlorination requires 30 minutes contact time with 50-200 mg/L
chlorine; reverse osmosis removes TDS .
8. Electrical & Safety – Lock-out/Tag-out required by OSHA 29 CFR 1910.147 when
servicing pumps; 1 HP = 746 watts; confined space entry requires atmospheric testing .
9. Pumping Tests – Step-discharge test: minimum 4 steps at 50-110% of design capacity;
constant-rate test: minimum 24 hours; recovery water levels recorded after pumping
stops .
10. Plumbness & Alignment – Casing >12 inches: maximum horizontal deviation ≤ ¾ ×
smallest casing ID per 100 ft; dummy test: 40-ft rigid apparatus, ½ inch smaller than
casing ID for ≤12-inch casing .
, Page 2 of 111
250 MCQs with Rationales
1. According to the NGWA Code of Excellence, what is the minimum depth to which casing
must be installed to provide a sanitary seal for a residential well?
A) 10 feet
B) 14 feet
C) 18 feet
D) 24 feet
Answer: C
Rationale: The NGWA Code of Excellence requires installing casing to at least an 18-foot depth
for sanitary sealing, followed by surface sealing and installation of a sanitary well cap to prevent
surface water and contaminant entry .
2. In the context of hydrogeology, what best describes the term "porosity"?
A) The ability of rock or soil to transmit water
B) The percentage of void space within a rock or soil that can hold water
C) The rate at which water moves through a material
D) The pressure exerted by water in an aquifer
Answer: B
Rationale: Porosity is the percentage of void spaces within a material, indicating how much
water it can potentially hold. It does not measure the ease of water movement—that is
permeability .
, Page 3 of 111
3. A well is drilled into a confined aquifer. What is the primary purpose of sealing the annular
space with grout?
A) To prevent loss of aquifer pressure only
B) To prevent vertical migration of contaminants into the confined aquifer
C) To prevent corrosion of the casing
D) To prevent entry of sand into the well
Answer: B
Rationale: Annular space grouting (minimum 10 ft in confined aquifers) seals off the annulus to
prevent water and contaminants from moving vertically between aquifers, protecting the
confined aquifer from surface contamination .
4. What property of water describes its resistance to flow and deformation, directly affecting
pump selection and energy requirements?
A) Density
B) Viscosity
C) Conductivity
D) Surface tension
Answer: B
Rationale: Viscosity measures a fluid's resistance to flow. Higher viscosity (e.g., cold water or
fluids with additives) creates more resistance, requiring more energy to pump, which directly
influences pump selection and system design .
, Page 4 of 111
5. What is the conversion factor for pressure (psi) to head (feet of water column) at sea level?
A) 1 psi = 1.00 ft of head
B) 1 psi = 2.31 ft of head
C) 1 psi = 4.33 ft of head
D) 1 psi = 7.00 ft of head
Answer: B
Rationale: At sea level, 1 psi equals 2.31 feet of water column. This conversion is fundamental
for calculating Total Dynamic Head and pump selection .
6. What grouting material is most commonly specified for well sealing to prevent
contamination?
A) Neat cement (Portland cement)
B) Bentonite clay (minimum 20% solids)
C) Bentonite-cement mixture
D) Sand and gravel
Answer: B
Rationale: Bentonite grout (20% solids minimum) is the preferred material for well sealing
because it swells upon hydration and provides a low-permeability seal. It is specified in NGWA
standards for annular space sealing .
7. In water systems, what does GPM stand for as a standard unit of measurement?
A) Gallons per meter
B) Gallons per minute
