Page 1 of 130
New Mexico (MS-3) Cesspools, Septic Tanks &
Sewers Exam Complete Preparation Kit Exam
QUESTIONS AND DETAILED SOLUTIONS
New Mexico Environment Department (NMED) rules (20.7.3 NMAC), Construction Industries Division
(CID) licensing requirements, wastewater treatment principles, safe excavation/ trenching, health &
safety standards (confined space, PPE), and environmental protection. The exam also tests materials,
installation methods, system design, hydraulics, system inspection, troubleshooting and advanced
treatment units. Mastering these topics will help you protect public health, ensure proper system
function and comply with state laws.
250 Multiple Choice Practice Questions with Rationales
1. A licensed MS-3 contractor is called to a home where the septic tank alarm is sounding and the
system shows no effluent flowing. What is the most likely cause of this issue?
A) Clogged inlet baffle
B) Failed pump or float switch
C) Overflowing cesspool
D) Broken sewer line
Correct Answer: B
Rationale: Alarms in pumped systems are often triggered by pump failure, blocked floats, or high-water
conditions; a failed pump prevents effluent movement and triggers the alarm.
, Page 2 of 130
2. When installing a new septic tank in New Mexico, what is the required minimum liquid capacity for a
three-bedroom residence?
A) 750 gallons
B) 900 gallons
C) 1,000 gallons
D) 1,250 gallons
Correct Answer: B
Rationale: NMED sizing guidelines specify that a three-bedroom residence requires a septic tank with at
least 900 gallons liquid capacity to handle the estimated wastewater flow from that number of
bedrooms.
3. An existing drainfield is showing signs of failure with ponding and odors. What is the most immediate
action a contractor should take to mitigate the problem?
A) Add more gravel around the pipes
B) Reduce water use in the home and inspect the system
C) Install a larger septic tank
D) Replace the entire drainfield immediately
, Page 3 of 130
Correct Answer: B
Rationale: Reducing water use lessens hydraulic load while the contractor evaluates the system; further
diagnosis (e.g., checking for clogs, measuring soil absorption) then guides the necessary repair.
4. In New Mexico, which agency has primary authority for issuing permits for on-site liquid waste
systems of less than 5,000 gallons per day?
A) Construction Industries Division (CID)
B) New Mexico Environment Department (NMED)
C) Local municipal building department
D) Office of the State Engineer
Correct Answer: B
Rationale: NMED’s Liquid Waste Program regulates domestic wastewater discharges to septic systems
under 5,000 gallons per day and issues the required permits.
5. A homeowner wants to install a conventional septic system themselves. What must they do first to be
allowed to perform this work under state rules?
A) Obtain a contractor’s license from CID
B) Pass a qualification exam administered by NMED
, Page 4 of 130
C) Hire a professional engineer to stamp the plans
D) Register as a maintenance service provider
Correct Answer: B
Rationale: Qualified homeowners may install or modify permitted conventional systems only after
successfully passing the homeowner qualification exam administered by NMED.
6. During a sewer line installation, you encounter a rock layer that prevents achieving the required
minimum slope. What is the most appropriate action to take?
A) Install the pipe at a reduced slope and note the deviation
B) Use a pump system to overcome the flat section
C) Excavate deeper to remove the rock layer
D) Reduce the pipe diameter to increase flow velocity
Correct Answer: B
Rationale: When gravity flow cannot be maintained because of site constraints, a pump (pressure)
system is required to move wastewater through the flat section. Reducing slope or pipe diameter will not
solve the hydraulic issue and may cause solids deposition.
New Mexico (MS-3) Cesspools, Septic Tanks &
Sewers Exam Complete Preparation Kit Exam
QUESTIONS AND DETAILED SOLUTIONS
New Mexico Environment Department (NMED) rules (20.7.3 NMAC), Construction Industries Division
(CID) licensing requirements, wastewater treatment principles, safe excavation/ trenching, health &
safety standards (confined space, PPE), and environmental protection. The exam also tests materials,
installation methods, system design, hydraulics, system inspection, troubleshooting and advanced
treatment units. Mastering these topics will help you protect public health, ensure proper system
function and comply with state laws.
250 Multiple Choice Practice Questions with Rationales
1. A licensed MS-3 contractor is called to a home where the septic tank alarm is sounding and the
system shows no effluent flowing. What is the most likely cause of this issue?
A) Clogged inlet baffle
B) Failed pump or float switch
C) Overflowing cesspool
D) Broken sewer line
Correct Answer: B
Rationale: Alarms in pumped systems are often triggered by pump failure, blocked floats, or high-water
conditions; a failed pump prevents effluent movement and triggers the alarm.
, Page 2 of 130
2. When installing a new septic tank in New Mexico, what is the required minimum liquid capacity for a
three-bedroom residence?
A) 750 gallons
B) 900 gallons
C) 1,000 gallons
D) 1,250 gallons
Correct Answer: B
Rationale: NMED sizing guidelines specify that a three-bedroom residence requires a septic tank with at
least 900 gallons liquid capacity to handle the estimated wastewater flow from that number of
bedrooms.
3. An existing drainfield is showing signs of failure with ponding and odors. What is the most immediate
action a contractor should take to mitigate the problem?
A) Add more gravel around the pipes
B) Reduce water use in the home and inspect the system
C) Install a larger septic tank
D) Replace the entire drainfield immediately
, Page 3 of 130
Correct Answer: B
Rationale: Reducing water use lessens hydraulic load while the contractor evaluates the system; further
diagnosis (e.g., checking for clogs, measuring soil absorption) then guides the necessary repair.
4. In New Mexico, which agency has primary authority for issuing permits for on-site liquid waste
systems of less than 5,000 gallons per day?
A) Construction Industries Division (CID)
B) New Mexico Environment Department (NMED)
C) Local municipal building department
D) Office of the State Engineer
Correct Answer: B
Rationale: NMED’s Liquid Waste Program regulates domestic wastewater discharges to septic systems
under 5,000 gallons per day and issues the required permits.
5. A homeowner wants to install a conventional septic system themselves. What must they do first to be
allowed to perform this work under state rules?
A) Obtain a contractor’s license from CID
B) Pass a qualification exam administered by NMED
, Page 4 of 130
C) Hire a professional engineer to stamp the plans
D) Register as a maintenance service provider
Correct Answer: B
Rationale: Qualified homeowners may install or modify permitted conventional systems only after
successfully passing the homeowner qualification exam administered by NMED.
6. During a sewer line installation, you encounter a rock layer that prevents achieving the required
minimum slope. What is the most appropriate action to take?
A) Install the pipe at a reduced slope and note the deviation
B) Use a pump system to overcome the flat section
C) Excavate deeper to remove the rock layer
D) Reduce the pipe diameter to increase flow velocity
Correct Answer: B
Rationale: When gravity flow cannot be maintained because of site constraints, a pump (pressure)
system is required to move wastewater through the flat section. Reducing slope or pipe diameter will not
solve the hydraulic issue and may cause solids deposition.
