Maintenance, Repair & Rehabilitation

Learn collection-system maintenance, repair, and rehabilitation, including preventive maintenance, spot repairs, lining, replacement, root and infiltration correction, emergency response, asset prioritization, records, and troubleshooting.

Collection-system maintenance, repair, and rehabilitation keep wastewater moving reliably while extending the useful life of sewers, manholes, pump stations, force mains, and related assets. Operators must know the difference between routine maintenance, localized repair, rehabilitation, and complete replacement so the response matches the actual condition of the asset.

Good collection-system management does not wait for repeated failures. Maintenance history, CCTV results, flow data, infiltration and inflow, blockage frequency, structural condition, and consequence of failure should be used together to decide where limited resources provide the greatest benefit.

Maintenance, Repair, Rehabilitation, and Replacement

These terms describe different levels of work.

Maintenance keeps an asset functioning without necessarily correcting major structural defects.

Repair corrects a specific defect or damaged location.

Rehabilitation restores or improves a larger portion of an existing asset and extends its useful life.

Replacement installs a new asset when the existing one can no longer be restored economically or reliably.

Examples of Maintenance

Maintenance can include:

sewer cleaning;
root cutting;
manhole cleaning;
valve exercising;
pump maintenance;
inspection;
lubrication.

Examples of Repair

Repairs can include:

fixing a broken pipe section;
sealing a leaking joint;
repairing a damaged manhole;
replacing a failed valve;
repairing a service connection.

Examples of Rehabilitation

Rehabilitation can include:

lining a sewer;
lining or coating a manhole;
grouting leaking joints;
renewing a larger section of deteriorated pipe.

When Replacement May Be Needed

Replacement may be appropriate when:

structural deterioration is severe;
collapse risk is high;
capacity is inadequate;
rehabilitation is not practical;
repeated repairs are no longer cost-effective.

Preventive Maintenance

Preventive maintenance is planned before a failure occurs.

Its goals include:

reducing emergency failures;
reducing sanitary sewer overflows;
extending asset life;
improving reliability;
reducing long-term cost.

Reactive Maintenance

Reactive maintenance occurs after a problem or failure is detected.

Examples include:

clearing an emergency blockage;
repairing a collapsed sewer;
replacing a failed pump;
repairing a broken force main.

Preventive Versus Reactive Work

Some reactive work is unavoidable, but a system that relies mainly on emergency response can experience:

higher costs;
more customer disruption;
more overflow risk;
less efficient use of crews.

Maintenance Planning

A maintenance program can use:

inspection history;
blockage history;
overflow history;
asset condition;
criticality;
manufacturer recommendations;
operating experience.

High-Frequency Maintenance Locations

Some sewer segments require more frequent work because of:

grease;
roots;
low slope;
sags;
heavy sediment;
recurring blockages.

Do Not Treat Recurring Failures as Independent Events

If the same asset fails repeatedly, operators should investigate the underlying cause rather than only restoring service each time.

Maintenance History Is Diagnostic Data

Repeated work can reveal:

progressive deterioration;
persistent hydraulic problems;
structural defects;
poor previous repairs.

Sewer Cleaning as Maintenance

Cleaning can restore flow area by removing:

grease;
roots;
grit;
sediment;
debris.

Cleaning Does Not Correct Structural Damage

A cracked, deformed, or collapsed sewer may continue to fail even after cleaning.

Root Control

Root cutting can restore hydraulic capacity, but recurring roots usually indicate an unresolved entry point.

The underlying defect may require:

joint repair;
lining;
spot repair;
replacement.

Grease Control

Recurring grease blockages may require both:

sewer cleaning;
source-control measures.

Spot Repair

A spot repair corrects a localized defect while leaving most of the sewer in place.

Spot repairs may be appropriate for:

isolated breaks;
severe joint defects;
localized collapse;
damaged service connections.

Open-Cut Repair

Open-cut repair requires excavation to expose the sewer.

It can provide direct access to:

replace damaged pipe;
correct alignment;
repair service connections;
restore bedding.

Open-Cut Limitations

Open excavation can involve:

traffic disruption;
utility conflicts;
surface restoration;
trench safety;
higher disruption in developed areas.

Trenchless Rehabilitation

Trenchless methods can rehabilitate sewer pipe with less excavation than traditional replacement.

Methods can include:

cured-in-place pipe lining;
other approved lining systems;
pipe bursting where replacement is required.

Cured-in-Place Pipe

Cured-in-place pipe, often called CIPP, creates a new liner inside the existing sewer.

Potential benefits can include:

improved structural condition;
reduced infiltration;
smoother interior surface;
less surface excavation.

Existing Pipe Preparation

Before lining, the existing sewer generally must be evaluated and prepared.

This can include:

cleaning;
CCTV inspection;
root removal;
service identification;
removal of major obstructions.

Service Connections After Lining

Service laterals must be properly reopened or reconnected after rehabilitation where applicable.

Improper reopening can create:

customer service loss;
hydraulic restriction;
future maintenance problems.

Post-Rehabilitation Inspection

CCTV after rehabilitation can verify:

liner condition;
service reconnections;
absence of major wrinkles or obstructions;
completion quality.

Pipe Bursting

Pipe bursting can replace an existing sewer by breaking the old pipe outward while pulling a new pipe into its path.

This method can reduce excavation compared with full open-cut replacement.

Pipe Bursting Is Not Suitable Everywhere

Site-specific factors include:

existing utilities;
service connections;
pipe material;
available access;
ground conditions.

Joint Sealing and Grouting

Some leaks can be corrected by sealing or grouting defective joints or surrounding soil pathways.

The objective can include reducing:

infiltration;
soil migration;
root entry.

Manhole Rehabilitation

Manholes may require rehabilitation because of:

infiltration;
corrosion;
cracking;
deteriorated joints;
poor frames and covers.

Manhole Coatings and Linings

Protective systems can be used to restore surfaces and protect against aggressive wastewater environments where appropriate.

Manhole Frame and Cover Repair

Frame and cover problems can create:

stormwater inflow;
traffic hazards;
access problems.

Infiltration Repairs

Reducing groundwater infiltration may require:

joint sealing;
pipe lining;
manhole sealing;
service-lateral rehabilitation;
spot repair.

Inflow Correction

Direct inflow may require correction of:

roof-drain connections;
sump-pump connections;
storm connections;
low or leaking manhole covers.

Verify I&I Reduction

After rehabilitation, flow monitoring should be used where appropriate to verify that wet-weather flow actually decreased.

Repair Success Should Be Measured

A completed construction project is not automatically a successful rehabilitation project.

Operators should compare:

pre-repair condition;
post-repair condition;
flow response;
maintenance frequency;
overflow history.

Force-Main Maintenance

Force-main maintenance can include:

valve inspection;
air-release valve maintenance;
pressure monitoring;
leak investigation;
corrosion assessment.

Force-Main Leaks

Possible warning signs include:

pressure loss;
reduced downstream flow;
wet ground;
wastewater surfacing.

Force-Main Repair

A force-main failure can require rapid coordination of:

pump-station shutdown;
bypass pumping;
excavation;
spill control;
repair crews.

Pump-Station Maintenance

Pump stations require preventive maintenance on:

pumps;
motors;
check valves;
isolation valves;
level controls;
alarms;
generators.

Backup Equipment

Redundant pumps and generators provide little protection if they are not maintained and tested.

Valve Exercising

Valves should be operated according to maintenance procedures so they remain functional when isolation is needed.

Asset Failure Consequences

Failure consequences can include:

customer backups;
sanitary sewer overflows;
environmental impact;
traffic disruption;
emergency repair cost.

Risk-Based Maintenance

A useful asset-management concept is:

Risk = Likelihood of Failure × Consequence of Failure

Likelihood of Failure

Likelihood can be influenced by:

asset condition;
age;
material;
failure history;
environment;
maintenance history.

Consequence of Failure

Consequence can depend on:

number of customers affected;
overflow potential;
environmental sensitivity;
traffic disruption;
repair difficulty;
lack of alternate flow path.

Critical Assets

A critical sewer or pump station may deserve priority even if its present condition is not the worst in the system.

Condition Alone Should Not Set Priority

A severely deteriorated small sewer in a low-consequence location may not have the same priority as a moderately deteriorated interceptor serving a major portion of the system.

Emergency Repair Planning

Operators should know how to respond to:

sewer collapse;
force-main break;
pump-station failure;
major blockage.

Emergency Response Resources

Useful resources can include:

portable pumps;
bypass piping;
excavation contractors;
repair materials;
traffic-control equipment;
spill-response supplies.

Bypass Pumping

Bypass pumping may be necessary while:

a sewer is repaired;
a pump station is out of service;
a force main is repaired;
rehabilitation work is performed.

Bypass Capacity

The bypass system should be able to handle expected wastewater flow with appropriate operational reliability.

Emergency Storage Time

If pumping stops, available storage time can be estimated as:

Remaining Time = Available Volume ÷ Incoming Flow

Emergency Storage Example

A pump station has 18,000 gallons of usable remaining wet-well storage.

Incoming flow is 600 gpm.

Remaining Time = 18,000 ÷ 600

Remaining Time = 30 minutes

This calculation assumes incoming flow remains constant and no wastewater is pumped out.

Repair Prioritization

Operators can prioritize work using:

condition;
failure risk;
overflow history;
customer impacts;
maintenance frequency;
cost;
available funding.

Short-Term Versus Long-Term Correction

An emergency cleaning or temporary patch can restore service, but a long-term repair may still be required.

Temporary Repair

Temporary repairs should be tracked so they are not forgotten after the immediate emergency ends.

Capital Improvement Planning

Large rehabilitation and replacement projects are often planned over multiple years.

Useful planning data include:

CCTV condition;
failure history;
I&I contribution;
capacity problems;
maintenance cost.

Life-Cycle Thinking

The lowest immediate repair cost is not always the lowest long-term cost.

Repeated emergency repairs can eventually cost more than rehabilitation or replacement.

Example: Sewer Requires Root Cutting Every Two Months

Review whether long-term correction of the root entry point is more appropriate than continuing frequent cutting.

Example: Sewer Has Heavy Infiltration but Good Structural Shape

Possible options may include:

joint sealing;
lining;
targeted leak repair.

Example: Sewer Has Severe Collapse Risk

Cleaning alone is not an adequate long-term response.

Repair, rehabilitation, or replacement should be evaluated promptly.

Example: New Liner Stops Repeated Root Blockages

Review maintenance history after rehabilitation to verify that blockage frequency actually declined.

Example: Wet-Weather Flow Does Not Improve After Main-Line Lining

Possible remaining I&I sources include:

service laterals;
manholes;
direct inflow connections.

Example: Pump Station Requires Frequent Emergency Repairs

Review:

pump age;
maintenance history;
run hours;
parts availability;
replacement economics.

Example: Force Main Has Repeated Leaks

Repeated failures may indicate:

corrosion;
material deterioration;
pressure problems;
need for broader rehabilitation or replacement.

Example: Repaired Sewer Still Blocks

Review whether the original repair corrected the true cause.

Possible remaining issues include:

upstream grease;
downstream restriction;
sag;
another root entry point.

Example: Maintenance Frequency Is Increasing

This can indicate deteriorating asset condition or worsening hydraulic problems.

Example: One Sewer Has No Failures but Very High Consequence

High criticality may justify more frequent inspection even without a recent failure.

Repair Documentation

Useful records include:

asset identification;
failure date;
defect type;
repair method;
materials used;
contractor or crew;
post-repair inspection.

Update Asset Records

After repair or rehabilitation, update:

system maps;
asset condition;
installation or rehabilitation date;
inspection records;
maintenance schedule.

Post-Repair Verification

Verification can include:

CCTV;
flow monitoring;
pressure testing;
visual inspection;
maintenance trend review.

Maintenance Performance Measures

Utilities may track indicators such as:

blockages;
overflows;
repeat failures;
preventive work completed;
emergency work;
inspection coverage.

Trend Repeat Failures

Repeat failures can indicate that corrective actions are treating symptoms rather than causes.

Safety During Maintenance and Repair

Collection-system maintenance can involve:

confined spaces;
excavations;
traffic;
hazardous atmospheres;
moving equipment;
electrical hazards;
biological exposure.

Excavation Safety

Open-cut sewer repair can involve:

cave-in risk;
underground utilities;
water accumulation;
mobile equipment.

Confined-Space Safety

Manholes and wet wells may contain:

hydrogen sulfide;
methane;
oxygen deficiency;
other hazardous atmospheres.

Lockout and Isolation

Before repairing pumps, valves, or mechanical equipment, applicable energy-isolation procedures should be followed.

Traffic Safety

Many collection-system repairs occur in roadways and require appropriate work-zone controls.

Common Maintenance, Repair, and Rehabilitation Mistakes

Using maintenance as a permanent substitute for structural repair.
Repeating root cutting without correcting the root entry point.
Repairing one leak without reviewing broader pipe condition.
Choosing rehabilitation based only on lowest initial cost.
Ignoring service laterals during I&I rehabilitation.
Failing to verify post-repair performance.
Prioritizing only by condition and ignoring consequence of failure.
Failing to track temporary repairs.
Failing to update asset records after rehabilitation.
Ignoring excavation, confined-space, traffic, electrical, and biological hazards.

A Practical Maintenance Review

Review asset condition.
Review blockage and overflow history.
Review cleaning frequency.
Review inspection results.
Identify recurring problems.
Determine whether routine maintenance is still appropriate.
Escalate assets needing repair or rehabilitation.

A Practical Repair Decision

Identify the exact defect.
Determine whether it is localized or widespread.
Review structural condition.
Review hydraulic impact.
Review I&I contribution.
Review failure consequence.
Compare repair, rehabilitation, and replacement options.
Select the response that addresses the underlying cause.

A Practical Rehabilitation Review

Inspect and document pre-rehabilitation condition.
Define the rehabilitation objective.
Select an appropriate method.
Prepare the asset properly.
Complete the rehabilitation.
Inspect completed work.
Verify service connections and hydraulic condition.
Update asset records and future maintenance plans.

A Practical Emergency-Failure Review

Protect workers and the public.
Control or bypass wastewater flow.
Prevent or limit overflow.
Identify the failed asset.
Complete temporary or permanent repair.
Restore normal operation.
Inspect the surrounding asset condition.
Document the failure and root cause.
Determine whether broader rehabilitation is needed.

A Practical Risk-Based Priority Review

Assess likelihood of failure.
Assess consequence of failure.
Review maintenance frequency.
Review overflow and backup history.
Review asset criticality.
Estimate repair or rehabilitation cost.
Prioritize the assets with the greatest combined operational risk.

What to Remember for the Exam

Maintenance keeps assets functioning, repair corrects specific defects, rehabilitation restores larger portions of existing assets, and replacement installs new assets.
Preventive maintenance is planned before failure, while reactive maintenance occurs after a problem develops.
Repeated failures should trigger investigation of the underlying cause.
Cleaning restores hydraulic capacity lost to deposits but does not correct structural defects.
Recurring roots usually indicate an unresolved crack, joint, or connection defect.
Spot repair is appropriate for certain localized defects.
Open-cut repair provides direct access but can create excavation, traffic, and restoration impacts.
Trenchless rehabilitation can restore sewer condition with less excavation.
CIPP creates a new liner inside an existing sewer.
Post-rehabilitation CCTV helps verify liner and service-connection condition.
Manhole rehabilitation can address infiltration, corrosion, cracking, and structural deterioration.
I&I rehabilitation should be verified with post-repair monitoring when appropriate.
Force mains, pump stations, valves, alarms, generators, and level controls require preventive maintenance.
Risk considers both likelihood of failure and consequence of failure.
Condition alone should not determine maintenance or rehabilitation priority.
Critical assets may require greater attention even when they have not failed recently.
Emergency bypass pumping may be necessary during sewer, pump-station, or force-main failures.
Available emergency storage time equals usable volume divided by incoming flow.
Repair and rehabilitation records should be added to the asset-management history.
Good collection-system management combines preventive maintenance, condition assessment, repair, rehabilitation, risk-based prioritization, emergency planning, accurate records, post-repair verification, and safe work practices.