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Idaho Division of Occupational and Professional Licenses — Installer Registration exam Qu, Exams of Water and Wastewater Engineering

Idaho State University (ISU)Water and Wastewater Engineering

Idaho Division of Occupational and Professional Licenses — Installer Registration exam Questions And Correct Answers Plus Rationales 2025.

Typology: Exams

2024/2025

Available from 07/02/2025

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Idaho Division of Occupational and Professional Licenses
— Installer Registration exam Questions And Correct
Answers Plus Rationales 2025.
1. What is the minimum setback distance for a septic tank from a domestic
well in Idaho?
100 feet
This distance helps protect groundwater from contamination by ensuring
adequate separation between the well and the septic tank.
2. What is the minimum depth of soil required below a drainfield trench in
Idaho?
4 feet
This ensures there is enough unsaturated soil to treat effluent before it reaches
the water table.
3. A new septic system must be designed to handle what percentage of the
estimated daily flow?
100%
The system must be designed for the full estimated daily sewage flow to prevent
overflow or failure.
4. Which Idaho code governs the installation of onsite wastewater treatment
systems?
IDAPA 58.01.03
This is the Idaho Department of Environmental Quality’s administrative rules for
individual and subsurface sewage disposal.
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Download Idaho Division of Occupational and Professional Licenses — Installer Registration exam Qu and more Exams Water and Wastewater Engineering in PDF only on Docsity!

Idaho Division of Occupational and Professional Licenses

— Installer Registration exam Questions And Correct

Answers Plus Rationales 2025.

  1. What is the minimum setback distance for a septic tank from a domestic well in Idaho? 100 feet This distance helps protect groundwater from contamination by ensuring adequate separation between the well and the septic tank.
  2. What is the minimum depth of soil required below a drainfield trench in Idaho? 4 feet This ensures there is enough unsaturated soil to treat effluent before it reaches the water table.
  3. A new septic system must be designed to handle what percentage of the estimated daily flow? 100% The system must be designed for the full estimated daily sewage flow to prevent overflow or failure.
  4. Which Idaho code governs the installation of onsite wastewater treatment systems? IDAPA 58.01. This is the Idaho Department of Environmental Quality’s administrative rules for individual and subsurface sewage disposal.
  1. What is the maximum slope allowed for a drainfield site? 25% Slopes greater than this may cause effluent to surface or run off without proper soil treatment.
  2. Which soil type provides the best percolation for a drainfield? Loamy sand Loamy sand has good permeability for treating effluent while preventing rapid percolation.
  3. When must an installer notify the Health District before beginning work? Before any excavation begins This allows for necessary inspections and verification that the installation meets approved plans.
  4. What is the minimum septic tank capacity for a 3-bedroom home in Idaho? 1,000 gallons This size accommodates typical daily sewage flows and allows for proper settling of solids.
  5. Who must inspect the septic installation before backfilling? The local Health District inspector Inspection ensures that the system is installed according to approved plans and regulations.
  6. Which component separates solids from liquids in a septic system? Septic tank The septic tank allows solids to settle and scum to rise, producing partially clarified effluent.
  1. What is the maximum depth for a conventional drainfield trench? 3 feet This depth allows effluent to be properly treated by the unsaturated soil zone.
  2. What is the minimum distance between drainfield trenches? 6 feet This spacing ensures adequate soil absorption area and prevents overlapping zones of saturation.
  3. Which sign indicates a failing drainfield? Effluent surfacing on the ground Surfacing effluent shows that the soil is not absorbing wastewater properly.
  4. What is the role of distribution boxes? Distribute effluent evenly Distribution boxes ensure effluent is evenly distributed across all drainfield trenches.
  5. What must be done with excavated soil? Spread and grade properly Proper grading prevents ponding and directs surface water away from the system.
  6. How should pipes in a drainfield trench be installed? Level or with slight slope A slight slope ensures uniform distribution without pooling or rapid flow.
  7. What is the required setback from a septic tank to a dwelling? 10 feet This separation minimizes the risk of sewage backflow into the home.
  8. Who is responsible for submitting the final installation report? The installer

The installer must verify that the system was installed according to the approved plan.

  1. When must an installer renew their registration? Annually Installer registration must be kept current to perform installations legally.
  2. Which type of system is required for high groundwater areas? Mound system Mound systems elevate the drainfield above natural grade to ensure proper treatment in high groundwater areas.
  3. How are drainfield trenches backfilled? With native soil free of large rocks This protects the pipes and maintains good soil structure for percolation.
  4. What is a key benefit of using chamber systems? Increased infiltration area Chamber systems can increase infiltration surface area compared to gravel trenches.
  5. What must be protected from vehicular traffic? Septic tanks and drainfields Traffic can damage pipes and compact soil, reducing system performance.
  6. What does an effluent pump do? Moves wastewater to higher elevation Effluent pumps lift treated wastewater when gravity flow is not possible.
  7. When can a system be used after installation? After final inspection and approval The system must pass inspection before it is put into service.
  1. What is a common cause of drainfield failure? Overloading with excessive water Too much water overwhelms the soil’s ability to treat effluent.
  2. What is the main goal of setback requirements? Protect public health and water quality Proper setbacks prevent contamination of wells and surface water.
  3. Which material is prohibited in drainfield construction? Clay soil Clay does not percolate well and can cause system failure.
  4. What must installers do to prevent trench collapse? Follow OSHA excavation safety rules Excavation safety protects workers and ensures code compliance.
  5. What must be done if a drainfield is abandoned? Properly decommissioned Abandoned systems must be decommissioned to prevent health hazards.
  6. What happens if setbacks cannot be met? An alternative system must be designed Engineered alternatives can accommodate difficult site conditions.
  7. How often must effluent pumps be serviced? According to manufacturer’s recommendations Regular maintenance ensures pump reliability.
  8. What is the required setback for a drainfield from a domestic well? 100 feet This distance prevents contamination of drinking water supplies.
  1. What is the minimum pipe diameter for effluent lines? 4 inches This size prevents clogging and allows for adequate flow.
  2. What is the installer’s first step before installation? Review approved plans and permits This ensures the work meets design and code requirements.
  3. How should surface water be managed around the system? Diverted away from tank and drainfield Keeping surface water away reduces the risk of system flooding and failure.
  4. What must be done before installing a replacement system? Obtain a new permit A new permit ensures the replacement meets current codes and site conditions.
  5. What is required if bedrock is encountered during excavation? Stop work and consult the Health District Bedrock may limit soil treatment; approval for an alternative design may be needed.
  6. What does IDAPA stand for? Idaho Administrative Procedures Act This is the body of rules that governs professional licensing and onsite wastewater rules.
  7. What material is commonly used for septic tank baffles? Concrete or PVC These materials are durable and resist corrosion from wastewater.
  1. When must an installer replace broken distribution pipes? Immediately, before backfilling Damaged pipes can cause uneven distribution and system failure.
  2. What does a drop box do? Controls flow to sequential trenches Drop boxes help distribute effluent evenly in serial systems.
  3. What is the setback for a drainfield from a stream or pond? 100 feet This prevents direct contamination of surface water bodies.
  4. What is an advantage of using PVC pipe in drainfields? Resistant to corrosion PVC lasts longer underground compared to metal pipes.
  5. How should backfill be placed around pipes? Carefully, by hand if needed This prevents damage to pipes and ensures proper grading.
  6. What is a curtain drain used for? Diverting groundwater away from the drainfield Curtain drains help maintain unsaturated soil conditions.
  7. What does a dosing tank do? Stores and pumps effluent It delivers effluent in doses to the drainfield for better performance.
  8. What is the minimum setback from an interceptor drain to a drainfield? 10 feet This prevents short-circuiting of treated effluent.
  1. What must be done with construction debris? Removed from site Debris can interfere with system function and inspection.
  2. What should be done if septic odors are detected near a system? Inspect for leaks or surfacing effluent Odors can indicate a malfunction or improper venting.
  3. What is the first sign of hydraulic overloading? Slow drains or backups Hydraulic overloading occurs when too much water enters the system.
  4. Who approves the final system design? Local Health District Only the local authority can approve system plans and issue permits.
  5. What is used to prevent soil erosion over drainfields? Grass cover Grass stabilizes soil without interfering with system performance.
  6. Which pipe is best for connecting tank to drainfield? Schedule 40 PVC This pipe is durable and designed for underground use.
  7. What must be done to protect tanks in freezing climates? Insulate or bury below frost line This prevents freezing and system failure in winter.
  8. When are serial distribution systems used? On sloping sites Serial systems distribute effluent sequentially down slope.
  1. What must an installer do before installing on frozen ground? Obtain Health District approval Frozen ground can damage pipes and affect performance.
  2. What does ponding in trenches indicate? Soil is clogged or overloaded Ponding shows the system is not absorbing effluent properly.
  3. What must be done when a tank is abandoned? Pumped and filled or removed This prevents safety hazards and contamination.
  4. How should effluent be distributed in a trench? Evenly across the entire length This maximizes treatment area and prevents overload.
  5. What can cause a drainfield to freeze? Lack of vegetative cover Exposed soil allows frost to penetrate more deeply.
  6. How can trees affect a septic system? Roots may clog pipes Roots seek moisture and can damage drainfields.
  7. When is a site evaluation required? Before design approval Site evaluations assess soil, slopes, and constraints.
  8. What does TSS stand for in wastewater? Total Suspended Solids High TSS can clog systems and affect treatment.
  1. How often should effluent filters be inspected? Every year Annual inspection prevents clogs and backups.
  2. What is the setback for a septic tank from a foundation drain? 10 feet This keeps wastewater from entering drains.
  3. What is the best practice for tank lids? Watertight and lockable This prevents unauthorized access and leaks.
  4. What is the main function of a baffle? Direct flow and retain solids Baffles keep solids from leaving the tank.
  5. What should be done if a pipe slope is too steep? Re-grade to proper slope Too steep a slope can cause solids to settle and block flow.
  6. What does “hydraulic loading rate” refer to? Volume applied per area per day It determines how much effluent soil can accept.
  7. How can installers prevent soil compaction? Limit heavy equipment use Compaction reduces soil permeability.
  8. What is the minimum setback for a drainfield from a road? 5 feet This prevents damage and maintains access.
  1. Which factor most affects soil absorption? Soil texture Texture determines how fast water moves through.
  2. What must be done when replacing a failed drainfield? Decommission old one properly Abandoned systems must be rendered safe.
  3. What is used to disperse effluent evenly in a trench? Gravel or chambers They increase infiltration surface area.
  4. What causes scum buildup? Fats, oils, grease These float and form a scum layer.
  5. What protects against backflow? Backwater valve Prevents sewage from re-entering the building.
  6. What is the setback from a drainfield to a down-gradient well? 200 feet Extra distance protects well water quality.
  7. What must be done if trench bottoms are smeared? Scarify trench bottom Loosening prevents compaction that impedes infiltration.
  8. What is the function of a pump alarm? Alert when pump fails Alarms prevent backups and system damage.
  1. Which pipe slope is acceptable for gravity sewer lines? 2% A 2% slope ensures flow and prevents blockages.
  2. What does “serial distribution” mean? Effluent flows from trench to trench Used on slopes to manage flow.
  3. What is the setback from a septic tank to a surface water body? 50 feet This reduces the risk of direct contamination.
  4. What is the minimum number of tanks for large flows? Two or more in series Multiple tanks improve treatment.
  5. What does a watertight riser do? Provides secure access Prevents surface water from entering.
  6. What happens if the drainfield is undersized? System will fail prematurely An undersized system can’t treat the design flow.
  7. How deep should distribution pipes be set? About 18–24 inches below grade Depth varies by local code and site.
  8. What is the best cover for a sand mound? Grass Grass prevents erosion without deep roots.
  1. How should observation ports be finished above grade? Capped and secured This prevents debris or animals from entering.
  2. Which system is best for shallow soils over fractured bedrock? Sand mound Mounds provide additional treatment depth above shallow soil.
  3. What causes saturated soil conditions? Excessive water loading Too much water can overwhelm the soil’s capacity to absorb effluent.
  4. What is the maximum allowable depth of ponding in an observation port? 0 inches Standing water in a port means the system is failing.
  5. What does “biomat” do in a drainfield? Helps treat wastewater The biomat filters and breaks down pollutants but can clog if overloaded.
  6. How often should dosing tanks be inspected? Annually Regular inspections help identify pump or float issues.
  7. What is the setback from a drainfield to a swimming pool? 15 feet Prevents cross-contamination and structural damage.
  8. What does a sand-lined trench do? Improves soil treatment Sand lining adds a filtering layer in poor soils.
  1. What is the setback distance from a septic tank to a storm drain? 25 feet Protects storm drains from contamination.
  2. What is the best way to prevent tree roots from infiltrating a drainfield? Plant grass only Deep-rooted plants can clog or damage pipes.
  3. Who is responsible for system maintenance? The property owner The owner must ensure regular pumping and repairs.
  4. What is the slope limit for a mound system? 12% Slopes steeper than this can cause mound instability.
  5. Which tool is used to measure tank depth? Measuring rod or tape Accurate measurement is important for installation and inspection.
  6. What is the primary indicator of seasonal high groundwater? Soil mottling Mottling shows where water levels fluctuate annually.
  7. Which system allows for alternating drainfields? Diverter valve system Alternating fields prolong system life by allowing rest periods.
  8. How should a trench bottom be finished? Level and scarified This prevents compaction and promotes infiltration.