Texas Wastewater Collection System
Operator Class I Exam 2025/2026 – Verified
Test Questions with Detailed Rationales and
Correct Answers for Certification Success
Introduction
This document provides over 100 verified practice questions for the Texas Wastewater
Collection System Operator Class I certification exam. Each question includes the correct
answer and a detailed rationale to aid in understanding key concepts. The focus is on core
topics such as system components, maintenance, safety, flow management, and
regulations. Questions are numbered sequentially for easy reference. Study these to build
confidence for the 2025/2026 exam.
Practice Questions
1. Question: What is the primary purpose of a wastewater collection system?
Correct Answer: To transport wastewater to a treatment facility.
Rationale: The collection system gathers wastewater from homes, businesses, and
industries via pipes and pumps, directing it to a treatment plant where
contaminants are removed to protect public health and the environment. This
prevents untreated discharge into natural water bodies.
2. Question: What type of pipe is commonly used in gravity sewer systems?
Correct Answer: PVC (Polyvinyl Chloride).
,Rationale: PVC pipes are lightweight, corrosion-resistant, and have a smooth interior that
promotes efficient flow with minimal friction. They are cost-effective and widely available
for residential and small municipal systems.
3. Question: What is the minimum slope for a 6-inch gravity sewer pipe?
Correct Answer: 0.01 ft/ft.
Rationale: A minimum slope of 0.01 feet per foot ensures a self-cleansing velocity of at
least 2 feet per second, preventing solids deposition and maintaining flow without
excessive erosion.
4. Question: What is the main cause of sewer backups in residential areas?
Correct Answer: Blockages.
Rationale: Blockages from grease buildup, tree roots, wipes, or debris restrict flow,
causing upstream pressure buildup and overflows. Regular inspections and cleaning
mitigate this common issue.
5. Question: What is the purpose of a manhole in a sewer system?
Correct Answer: Access for inspection and maintenance.
Rationale: Manholes provide entry points for workers to visually inspect pipes, remove
debris, sample flows, and perform repairs, ensuring system integrity without full
excavation.
6. Question: Which of the following is considered a wastewater collection system
component?
Correct Answer: Lift station.
Rationale: Lift stations use pumps to elevate wastewater in areas where gravity flow is
insufficient, preventing low spots from causing backups and maintaining consistent
transport to downstream lines.
7. Question: What type of flow occurs when the pipe is only partially full?
Correct Answer: Gravity flow.
, Rationale: In gravity systems, pipes are designed to run partially full, relying on slope to
create velocity that scours the pipe bottom and transports solids effectively.
8. Question: What is an infiltration in a sewer system?
Correct Answer: Groundwater entering the sewer.
Rationale: Infiltration occurs through cracks, poor joints, or manhole walls during wet
weather, increasing flow volumes and treatment costs while diluting wastewater strength.
9. Question: What is an inflow in a sewer system?
Correct Answer: Stormwater entering the sewer through illegal connections.
Rationale: Inflow from roof leaders, downspouts, or sump pumps adds clear water
volume, overwhelming capacity during storms and risking overflows or treatment plant
surcharges.
10. Question: Why is it important to remove roots from sewer lines?
Correct Answer: They can block flow and damage pipes.
Rationale: Roots enter through joints seeking moisture, growing to obstruct flow and exert
pressure that cracks pipes, leading to leaks, collapses, and costly repairs.
11. Question: What type of maintenance involves cleaning sewer pipes to remove
debris and buildup?
Correct Answer: Preventive maintenance.
Rationale: Scheduled cleaning with rods, jets, or vacuums removes potential blockages
before they cause issues, extending pipe life and reducing emergency responses.
12. Question: What device is used to measure the flow of wastewater in a collection
system?
Correct Answer: Flow meter.
Rationale: Flow meters, such as weirs or magnetic types, quantify volumes for capacity
planning, billing, and compliance with TCEQ discharge limits.
Operator Class I Exam 2025/2026 – Verified
Test Questions with Detailed Rationales and
Correct Answers for Certification Success
Introduction
This document provides over 100 verified practice questions for the Texas Wastewater
Collection System Operator Class I certification exam. Each question includes the correct
answer and a detailed rationale to aid in understanding key concepts. The focus is on core
topics such as system components, maintenance, safety, flow management, and
regulations. Questions are numbered sequentially for easy reference. Study these to build
confidence for the 2025/2026 exam.
Practice Questions
1. Question: What is the primary purpose of a wastewater collection system?
Correct Answer: To transport wastewater to a treatment facility.
Rationale: The collection system gathers wastewater from homes, businesses, and
industries via pipes and pumps, directing it to a treatment plant where
contaminants are removed to protect public health and the environment. This
prevents untreated discharge into natural water bodies.
2. Question: What type of pipe is commonly used in gravity sewer systems?
Correct Answer: PVC (Polyvinyl Chloride).
,Rationale: PVC pipes are lightweight, corrosion-resistant, and have a smooth interior that
promotes efficient flow with minimal friction. They are cost-effective and widely available
for residential and small municipal systems.
3. Question: What is the minimum slope for a 6-inch gravity sewer pipe?
Correct Answer: 0.01 ft/ft.
Rationale: A minimum slope of 0.01 feet per foot ensures a self-cleansing velocity of at
least 2 feet per second, preventing solids deposition and maintaining flow without
excessive erosion.
4. Question: What is the main cause of sewer backups in residential areas?
Correct Answer: Blockages.
Rationale: Blockages from grease buildup, tree roots, wipes, or debris restrict flow,
causing upstream pressure buildup and overflows. Regular inspections and cleaning
mitigate this common issue.
5. Question: What is the purpose of a manhole in a sewer system?
Correct Answer: Access for inspection and maintenance.
Rationale: Manholes provide entry points for workers to visually inspect pipes, remove
debris, sample flows, and perform repairs, ensuring system integrity without full
excavation.
6. Question: Which of the following is considered a wastewater collection system
component?
Correct Answer: Lift station.
Rationale: Lift stations use pumps to elevate wastewater in areas where gravity flow is
insufficient, preventing low spots from causing backups and maintaining consistent
transport to downstream lines.
7. Question: What type of flow occurs when the pipe is only partially full?
Correct Answer: Gravity flow.
, Rationale: In gravity systems, pipes are designed to run partially full, relying on slope to
create velocity that scours the pipe bottom and transports solids effectively.
8. Question: What is an infiltration in a sewer system?
Correct Answer: Groundwater entering the sewer.
Rationale: Infiltration occurs through cracks, poor joints, or manhole walls during wet
weather, increasing flow volumes and treatment costs while diluting wastewater strength.
9. Question: What is an inflow in a sewer system?
Correct Answer: Stormwater entering the sewer through illegal connections.
Rationale: Inflow from roof leaders, downspouts, or sump pumps adds clear water
volume, overwhelming capacity during storms and risking overflows or treatment plant
surcharges.
10. Question: Why is it important to remove roots from sewer lines?
Correct Answer: They can block flow and damage pipes.
Rationale: Roots enter through joints seeking moisture, growing to obstruct flow and exert
pressure that cracks pipes, leading to leaks, collapses, and costly repairs.
11. Question: What type of maintenance involves cleaning sewer pipes to remove
debris and buildup?
Correct Answer: Preventive maintenance.
Rationale: Scheduled cleaning with rods, jets, or vacuums removes potential blockages
before they cause issues, extending pipe life and reducing emergency responses.
12. Question: What device is used to measure the flow of wastewater in a collection
system?
Correct Answer: Flow meter.
Rationale: Flow meters, such as weirs or magnetic types, quantify volumes for capacity
planning, billing, and compliance with TCEQ discharge limits.
