Inspection & Condition Assessment

Collection-system inspection and condition assessment help operators find defects before they become blockages, backups, overflows, collapses, or major repair emergencies. Inspection provides information about the actual condition of pipes, manholes, service connections, pump-station structures, and other collection-system assets.

Effective condition assessment is more than simply recording defects. Operators should identify what the defect means, whether it affects hydraulic performance or structural integrity, how quickly it may worsen, and whether maintenance, repair, rehabilitation, or continued monitoring is appropriate.

Purpose of Collection-System Inspection

Inspection helps operators:

• locate defects;
• identify maintenance needs;
• evaluate structural condition;
• identify infiltration and inflow;
• investigate repeated blockages;
• prioritize repairs;
• improve asset records.

Condition Assessment

Condition assessment is the systematic evaluation of an asset's physical and operational condition.

It can include information from:

• visual inspection;
• CCTV inspection;
• manhole inspection;
• flow monitoring;
• maintenance history;
• customer complaints;
• failure history.

Inspection Is Preventive

Waiting for a sewer to fail is usually more disruptive and expensive than identifying deterioration early.

Inspection can provide warning before:

• pipe collapse;
• major root blockage;
• severe infiltration;
• repeated sanitary sewer overflows.

Asset Inventory

Condition assessment begins with knowing what assets exist.

Useful asset information includes:

• location;
• pipe diameter;
• pipe material;
• installation date;
• manhole identification;
• service area;
• inspection history.

System Maps

Accurate maps help operators understand:

• flow direction;
• upstream and downstream connections;
• access locations;
• critical facilities;
• inspection routes.

Visual Surface Inspection

Surface inspection can identify problems without entering the sewer.

Operators may look for:

• sunken pavement;
• wet ground;
• odor;
• damaged manhole covers;
• surface settlement;
• wastewater surfacing.

Surface Settlement

Settlement above a sewer can indicate:

• soil loss;
• pipe failure;
• joint leakage;
• poor previous construction.

Unexpected Wet Areas

Wet ground during otherwise dry conditions can indicate:

• sewer leakage;
• water-main leakage;
• groundwater;
• other underground utility problems.

Manhole Inspection

Manholes provide important information about system condition.

An inspection can include:

• cover and frame condition;
• structural condition;
• corrosion;
• infiltration;
• channel condition;
• bench condition;
• flow observation;
• debris.

Manhole Cover

Inspect the cover for:

• cracks;
• damage;
• poor fit;
• missing components;
• evidence of surface-water entry.

Frame Condition

A damaged or poorly sealed frame can contribute to:

• inflow;
• structural deterioration;
• traffic hazards.

Manhole Wall Defects

Possible defects include:

• cracks;
• leaking joints;
• corrosion;
• missing mortar;
• exposed reinforcement.

Manhole Corrosion

Corrosion can be severe in areas exposed to hydrogen sulfide and other aggressive conditions.

Advanced corrosion can reduce structural strength.

Manhole Infiltration

Evidence of groundwater entry can include:

• visible streams;
• dripping;
• mineral deposits;
• wet joints.

Manhole Channel

Inspect the flow channel for:

• debris;
• erosion;
• poor alignment;
• sediment accumulation.

Manhole Bench

Benching should direct incidental water toward the channel.

Ponding or heavy deposits can indicate poor configuration or maintenance needs.

Flow Observation

Operators can often learn useful information by observing wastewater flow from the surface.

Look for:

• unusually high depth;
• low flow;
• backwater;
• turbulence;
• debris;
• unexpected clear water.

Unexpected Clear Water

Clear water entering a sanitary sewer can indicate:

• groundwater infiltration;
• stormwater inflow;
• another unintended connection.

High Upstream Level

A high level in one manhole with a much lower level downstream can indicate a restriction between the structures.

Closed-Circuit Television Inspection

CCTV inspection allows operators to view the interior of a sewer without entering it.

CCTV can identify:

• roots;
• cracks;
• broken pipe;
• joint defects;
• deformation;
• deposits;
• grease;
• standing water;
• service connections.

Clean Before CCTV When Appropriate

Heavy deposits can hide pipe defects.

Cleaning before inspection can improve visibility when the inspection objective requires a clear view of the pipe wall.

Pre-Cleaning Can Also Remove Evidence

If the goal is to determine why repeated deposits or blockages occur, the system may sometimes need to be documented before cleaning.

The inspection approach should match the purpose of the investigation.

CCTV Camera Orientation

Operators reviewing CCTV should know:

• inspection direction;
• starting manhole;
• ending manhole;
• distance into the pipe.

Record Defect Location

Defects should be documented by location so they can be found for repair.

Useful information includes:

• distance from access point;
• clock position where applicable;
• severity;
• type of defect.

Cracks

Pipe cracks can indicate:

• structural stress;
• settlement;
• aging;
• external loading.

Broken Pipe

Broken sections can create:

• soil entry;
• infiltration;
• blockages;
• collapse risk.

Pipe Collapse

A collapse can significantly reduce or completely block flow.

Warning signs can include:

• severe deformation;
• missing pipe wall;
• soil intrusion;
• repeated backups.

Joint Offset

A joint offset occurs when connected pipe sections are no longer properly aligned.

It can:

• reduce flow area;
• catch debris;
• allow infiltration;
• indicate settlement.

Open Joint

An open joint can create a pathway for:

• groundwater;
• roots;
• soil.

Root Intrusion

Roots commonly enter through:

• cracks;
• joints;
• service connections.

Root Severity

Minor roots may indicate an early defect.

Heavy root masses can:

• restrict flow;
• capture wipes and debris;
• cause recurring blockages.

Grease Deposits

Grease can accumulate on sewer walls and reduce effective diameter.

CCTV can help show:

• deposit thickness;
• location;
• extent of restriction.

Mineral Deposits

Mineral deposits can indicate:

• long-term infiltration;
• chemical conditions;
• reduced pipe area.

Grit and Sediment

Deposits at the bottom of a sewer can indicate:

• low velocity;
• poor slope;
• structural sag;
• high grit loading.

Standing Water

Standing water in a gravity sewer can indicate:

• sag;
• downstream restriction;
• poor grade;
• temporary blockage.

Distinguish Sag from Backwater

If standing water is caused by a structural low point, it may remain after downstream levels fall.

Backwater may change when downstream hydraulic conditions change.

Pipe Deformation

Flexible pipe can lose its intended circular shape.

Severe deformation can:

• reduce capacity;
• increase structural risk;
• interfere with cleaning equipment.

Service Connections

CCTV should document service connections and possible defects such as:

• protrusion;
• root entry;
• leakage;
• poor connection geometry.

Protruding Lateral

A service connection extending into the main can:

• catch debris;
• restrict cleaning equipment;
• reduce flow area.

Active Infiltration

CCTV may show water entering directly through:

• joints;
• cracks;
• service connections.

Inspection Timing Matters

Some defects are easier to observe:

• during high groundwater;
• after rainfall;
• during dry-weather low flow.

Structural Defects

Structural defects affect the physical integrity of the asset.

Examples include:

• cracks;
• fractures;
• collapse;
• deformation;
• severe corrosion.

Operational Defects

Operational defects affect sewer function without necessarily indicating immediate structural failure.

Examples include:

• grease;
• roots;
• sediment;
• debris;
• protruding laterals.

A Defect Can Be Both Structural and Operational

An open joint can:

• allow infiltration;
• allow root entry;
• indicate structural movement.

Condition Rating

Utilities may assign condition ratings to help prioritize work.

A rating system can consider:

• defect type;
• severity;
• frequency;
• likelihood of failure.

Condition Is Not the Same as Risk

A pipe can be in poor condition but have relatively low consequence if failure affects few customers.

Another pipe may have moderate defects but very high consequence because it serves a major facility or has no practical bypass.

Risk Concept

A common asset-management concept is:

Risk = Likelihood of Failure × Consequence of Failure

Likelihood of Failure

Factors can include:

• condition;
• age;
• material;
• failure history;
• environment.

Consequence of Failure

Factors can include:

• number of customers affected;
• overflow potential;
• environmental impact;
• traffic disruption;
• repair difficulty.

Critical Sewers

Some sewers deserve greater inspection frequency because failure would have major consequences.

Maintenance History

Maintenance records can reveal deterioration not obvious from one inspection.

Examples include:

• increasing cleaning frequency;
• repeated roots;
• repeated grease blockage;
• repeated backups.

Repeated Blockages Are Data

A location that repeatedly blocks should not automatically be treated as a series of unrelated events.

Investigate the underlying cause.

Customer Complaints

Complaints can provide useful information about:

• backups;
• odors;
• slow drainage;
• recurring local problems.

Flow Monitoring

Flow and depth data can supplement physical inspection.

Possible indications include:

• infiltration;
• inflow;
• surcharge;
• capacity loss.

Inspection After an Overflow

After an overflow, operators may inspect:

• blockage location;
• upstream and downstream sewer;
• roots;
• grease;
• structural condition.

Inspection After Cleaning

If a sewer requires frequent cleaning, CCTV after cleaning can help identify why material accumulates.

Inspection After Rehabilitation

Post-rehabilitation inspection can confirm:

• liner condition;
• service reconnections;
• absence of major defects;
• completion quality.

Inspection Frequency

Inspection frequency can be based on:

• asset condition;
• failure history;
• criticality;
• maintenance history;
• known I&I problems.

Not Every Sewer Needs the Same Frequency

A risk-based program focuses more attention on assets with higher likelihood or consequence of failure.

Manhole Identification

Each manhole should have a consistent identifier linked to system maps and records.

Pipe Segment Identification

Sewer segments can be identified by their upstream and downstream structures.

This makes inspection and maintenance records easier to connect to the correct asset.

Inspection Records

Useful inspection records include:

• date;
• asset identification;
• inspection method;
• defects;
• defect location;
• severity;
• recommended action.

Photos and Video

Visual records help:

• document current condition;
• compare deterioration over time;
• plan repairs;
• verify completed work.

Use Consistent Terminology

Consistent defect descriptions make inspection records easier to compare.

Trend Condition Over Time

Two inspections several years apart can show whether a defect is:

• stable;
• slowly worsening;
• rapidly deteriorating.

Example: Root Intrusion Appears Every Inspection

Repeated root growth can indicate an unresolved entry point such as:

• cracked pipe;
• open joint;
• defective lateral.

Example: Standing Water Increases Between Inspections

Possible causes include:

• progressive settlement;
• increasing downstream restriction;
• structural deformation.

Example: New Mineral Deposits Appear at a Joint

This can indicate chronic groundwater infiltration.

Example: Manhole Corrosion Worsens Rapidly

Review:

• hydrogen sulfide conditions;
• ventilation;
• upstream wastewater detention;
• force-main discharge conditions.

Example: Sewer Looks Structurally Sound but Blocks Frequently

Investigate operational causes such as:

• grease;
• roots;
• low velocity;
• wipes;
• service connection problems.

Example: Pipe Has Severe Defect but No Current Blockage

Absence of a blockage does not mean the defect can be ignored.

Structural failure risk should still be evaluated.

Example: Repeated Customer Backups but Main Sewer Appears Clear

Investigate:

• service laterals;
• private-side problems;
• intermittent downstream surcharge.

Example: CCTV Shows Heavy Deposits at One Low Point

Possible causes include:

• structural sag;
• poor original grade;
• settlement.

Example: Inspection Shows Active Groundwater Entry

Document:

• location;
• severity;
• flow conditions;
• possible repair method.

Example: Sewer Condition Is Good but Wet-Weather Flow Is High

Investigate other I&I sources such as:

• service laterals;
• manholes;
• private inflow connections.

From Inspection to Action

Inspection results should lead to one of several possible actions:

• no immediate action;
• increased monitoring;
• cleaning;
• root control;
• spot repair;
• rehabilitation;
• replacement.

Maintenance Versus Rehabilitation

Maintenance restores function without necessarily correcting structural deterioration.

Rehabilitation addresses defects to extend asset life or improve structural and hydraulic performance.

Cleaning Does Not Repair a Crack

Cleaning can remove deposits, but a structural defect may continue to allow:

• roots;
• infiltration;
• soil movement.

Root Cutting Does Not Seal the Entry Point

If roots repeatedly return, the underlying pipe or joint defect may require repair.

Prioritization

Work priorities can consider:

• defect severity;
• overflow history;
• customer impact;
• asset criticality;
• likelihood of failure;
• repair cost.

Emergency Defects

Conditions requiring rapid response can include:

• imminent collapse;
• severe blockage;
• active overflow;
• major structural failure.

Routine Defects

Less severe defects can be scheduled into planned maintenance or rehabilitation programs.

Inspection Safety

Collection-system inspection can involve:

• traffic;
• confined spaces;
• hazardous gases;
• biological exposure;
• moving inspection equipment.

Opening a Manhole

Even without entry, operators should recognize hazards from:

• traffic;
• heavy covers;
• unexpected gas release;
• fall hazards.

Manhole Entry

Entry into a manhole should follow applicable confined-space procedures.

CCTV Equipment Safety

Inspection vehicles, cables, reels, and powered equipment should be operated using applicable safety procedures.

Common Inspection and Condition-Assessment Mistakes

• Inspecting only after a failure occurs.
• Recording a defect without documenting its location.
• Cleaning repeatedly without investigating the cause of recurring deposits.
• Using one CCTV inspection without reviewing maintenance history.
• Assuming a structurally defective sewer is acceptable because flow currently passes.
• Ignoring service laterals and manholes during I&I investigations.
• Confusing condition with overall failure risk.
• Failing to compare inspections over time.
• Using inconsistent asset identifiers.
• Entering collection structures without appropriate safety procedures.

A Practical Manhole Inspection

1. Verify the manhole identification.
2. Establish safe traffic and work-zone conditions.
3. Inspect cover and frame condition.
4. Observe flow from the surface where safe.
5. Inspect visible structural condition.
6. Look for infiltration and corrosion.
7. Inspect channel and bench condition.
8. Document defects and recommended action.

A Practical CCTV Review

1. Verify the sewer segment identification.
2. Confirm inspection direction.
3. Record distance continuously.
4. Document roots, deposits, and grease.
5. Document cracks, joints, and deformation.
6. Document standing water and service connections.
7. Assign defect severity using the utility's method.
8. Recommend maintenance, repair, rehabilitation, or monitoring.

A Practical Recurring-Problem Review

1. Review blockage and cleaning history.
2. Review customer complaints.
3. Inspect the sewer after cleaning.
4. Identify structural and operational defects.
5. Review hydraulic conditions.
6. Determine why the problem returns.
7. Select an action that addresses the underlying cause.

A Practical Condition-Prioritization Review

1. Review defect severity.
2. Estimate likelihood of failure.
3. Evaluate consequence of failure.
4. Review overflow and backup history.
5. Review asset criticality.
6. Compare available maintenance and rehabilitation options.
7. Prioritize work according to risk and operational need.

Inverted Siphons: Inspection and Operational Assessment

An inverted siphon is a depressed section of a wastewater collection system in which sewage flows through a closed conduit under pressure from the available hydraulic head. Inverted siphons may be used to carry wastewater beneath waterways, roads, or other obstacles.

Although often called siphons, these facilities normally depend on upstream and downstream water levels and hydraulic head rather than conventional siphon suction.

Inverted Siphon Components and Flow Conditions

Operators should recognize the inlet structure, depressed conduits, outlet structure, access arrangements, and any installed provisions for flushing or isolation.

Some installations contain multiple barrels to accommodate varying flows and help maintain suitable velocities.

Because the conduit includes low points, settled solids and grit may accumulate when velocities are insufficient.

Monitor Hydraulic Performance

Observe upstream and downstream water levels, unusual surcharge conditions, recurring deposits, flow restrictions, odors, and maintenance history.

An increasing upstream level under comparable flow conditions may indicate excessive head loss, accumulated solids, or a developing restriction.

Interpret hydraulic observations with rainfall, upstream flow, and downstream conditions before identifying the cause.

Inspect and Investigate Problems

Inspect accessible structures for corrosion, structural damage, infiltration, debris, unusual deposits, and signs of abnormal hydraulic conditions.

Cleaning and internal inspection methods must be compatible with the installed conduit and available access points.

A conventional gravity-sewer CCTV procedure may not be appropriate when a conduit is submerged, pressurized, or cannot be safely isolated.

Use approved inspection methods and qualified personnel when specialized equipment or isolation is necessary.

Operational Risks and Corrective Action

Accumulated grit, grease, debris, or other obstructions can increase head loss and create upstream surcharge or overflow risks.

Operators should investigate recurring hydraulic problems and coordinate authorized cleaning, inspection, or repair activities.

Do not open a pressurized component or begin maintenance without confirming the required isolation and pressure-control procedures.

Remote Inspection Methods and Equipment Selection

Wastewater collection systems may be inspected using CCTV crawlers, push cameras, remotely operated inspection devices, and other authorized methods suited to the asset and site conditions.

Select an Appropriate Inspection Method

Choose inspection equipment based on pipe diameter, accessibility, flow depth, anticipated defects, environmental conditions, and the required inspection objective.

Remote inspection can reduce the need for personnel entry but does not eliminate hazards associated with opening manholes, traffic, electrical equipment, or confined spaces.

Specialized and Aerial Inspection

Where permitted and technically appropriate, remotely operated or aerial inspection systems may support assessment of accessible structures, surface conditions, outfalls, or difficult-to-reach infrastructure.

Drone inspection is not a universal replacement for internal sewer CCTV. Equipment suitability, visibility, access, operating restrictions, and required qualifications must be evaluated.

Inspection Quality and Documentation

Record the asset location, inspection method, relevant operating conditions, observed defects, and limitations that could affect the reliability of findings.

Use consistent defect descriptions and follow-up procedures so inspection results can support maintenance and rehabilitation decisions.

Exam reminder: Inverted siphons require attention to hydraulic head, solids deposition, access limitations, and safe cleaning. Remote inspection methods must be selected according to asset conditions and documented accurately.

Specialized Collection-System Inspection and Underground Utility Locating

Wastewater collection operators use specialized locating and inspection equipment to identify buried assets, support maintenance planning, and evaluate system components that cannot be adequately assessed by routine visual inspection alone.

Pipe Locators and Metal Detectors

Pipe and cable locators may use electromagnetic signals to help trace conductive buried utilities or a compatible transmitter or sonde placed in an accessible pipe or inspection device.

Operators should select the locating method according to the pipe material, available access, signal conditions, nearby utilities, and equipment capabilities.

Metal detectors can help identify metallic covers, fittings, and other buried metallic objects. They do not reliably establish the complete alignment or depth of every underground pipeline.

Before excavation, review available utility records, follow applicable utility-notification and locating requirements, and use approved methods to verify the location of underground facilities.

An electronic locator indication alone must not be treated as proof that excavation is safe.

Verify Underground Utility Locations

Compare locating results with system maps, GIS records, manhole locations, visible appurtenances, and known connections.

Unexpected signal changes, conflicting utility alignments, or missing structures require further investigation.

Where physical exposure is necessary, use authorized procedures and appropriate excavation methods, including suitable nondestructive methods where required.

Document the observed location, locating method, uncertainty, and any corrections needed in the asset records.

Manhole Guide Rollers and Inspection Equipment

Manhole guide rollers help direct suitable cables, hoses, or inspection equipment through an access opening while reducing abrasion against the structure.

Select compatible rollers and positioning arrangements for the equipment and access geometry. Inspect mounting hardware, rollers, cables, and contact surfaces before use.

Operators must keep hands and personnel clear of moving cables and pinch points, maintain equipment control, and follow applicable entry and traffic-control procedures.

Guide rollers do not eliminate confined-space hazards or make personnel entry unnecessary to evaluate.

Inspect Sluice Gates and Flow Regulators

Sluice gates and other collection-system control devices may be used to isolate flow paths or regulate flow according to facility design.

Inspect accessible components for corrosion, debris, leakage, damaged seals, abnormal movement, and indications of binding or incomplete closure.

For motor-operated or remotely controlled equipment, review position indications, alarms, operating limits, and the applicable control procedure.

A displayed gate position should be checked against available independent evidence when actual operating behavior is inconsistent with the indication.

Do not force a jammed gate, bypass protective controls, or open equipment exposed to uncontrolled hydraulic pressure.

Inspect Air-Release Devices and Other Special Structures

Collection-system inspection may include air-release devices, inlets, outfalls, overflow structures, regulators, inverted siphons, and associated access structures.

Evaluate the equipment according to its intended hydraulic function, observed system conditions, and manufacturer or facility procedures.

For force-main air-release equipment, investigate abnormal air accumulation, leakage, discharge conditions, corrosion, and accessibility. Maintenance must follow approved isolation and pressure-release procedures.

For inverted siphons, evaluate upstream surcharge, debris accumulation, flow restrictions, and access limitations using the dedicated inspection procedures described elsewhere in this article.

Document Findings and Prioritize Corrective Work

Record asset identification, location, equipment condition, observed defects, operating abnormalities, inspection limitations, and recommended corrective actions.

Prioritize problems according to likelihood of failure, service consequences, environmental risk, and safe access to the affected asset.

Exam reminder: Select locating and inspection methods according to the asset and equipment limitations. Verify underground utilities before excavation, use guide rollers safely, evaluate gates and regulators by their hydraulic function, and document inspection results for corrective maintenance.

What to Remember for the Exam

• Collection-system inspection identifies defects before they become major failures.
• Condition assessment combines physical inspection with operational and maintenance history.
• Manhole inspection can reveal structural defects, infiltration, corrosion, debris, and abnormal flow conditions.
• CCTV inspection allows detailed examination of sewer interiors without entry.
• Common CCTV findings include roots, cracks, joint defects, grease, deposits, deformation, standing water, and service-connection problems.
• Standing water can indicate sag, poor grade, or downstream backwater.
• Open joints and cracks can allow infiltration, root intrusion, and soil entry.
• Repeated root growth usually indicates an unresolved entry point.
• Structural defects affect asset integrity, while operational defects interfere with sewer function.
• A defect can have both structural and operational consequences.
• Condition is not the same as risk.
• Risk considers both likelihood of failure and consequence of failure.
• Maintenance history is valuable evidence during condition assessment.
• Repeated blockages should trigger investigation of the underlying cause.
• Flow monitoring can supplement physical inspection when evaluating I&I and capacity problems.
• Accurate asset identification and defect location are essential for future repair.
• Photos, video, and consistent records allow condition to be compared over time.
• Cleaning restores hydraulic function but does not repair structural defects.
• Inspection results should lead to appropriate monitoring, maintenance, repair, rehabilitation, or replacement.
• Good condition assessment combines inspection data, defect severity, hydraulic performance, maintenance history, asset criticality, safety, and risk-based prioritization.