Piping, Valves, Corrosion & Structural Maintenance

Learn maintenance fundamentals for piping, valves, corrosion, supports, coatings, concrete, steel, leaks, structural condition, and safe inspection in water and wastewater facilities.

Piping, valves, supports, tanks, concrete structures, and steel components form the physical backbone of water and wastewater facilities. These assets may deteriorate slowly, so routine inspection is important for finding corrosion, leakage, movement, cracking, coating failure, and valve problems before they become major failures.

Operators should understand common deterioration patterns and know when a condition can be monitored, when a work order is needed, and when immediate action is required.

Piping Maintenance

Piping maintenance focuses on preserving:

pressure integrity;
flow capacity;
structural support;
joint condition;
corrosion protection;
safe isolation capability.

Common Piping Problems

Common problems include:

external corrosion;
internal corrosion;
leaks;
cracks;
damaged joints;
failed supports;
vibration;
settlement;
erosion;
blockage.

External Corrosion

External corrosion occurs on the outside surface of metal piping or equipment.

Contributing conditions may include:

water exposure;
high humidity;
chemical vapors;
damaged coating;
soil contact;
poor drainage.

Internal Corrosion

Internal corrosion occurs on surfaces exposed to the process fluid.

Its severity depends on factors such as:

water chemistry;
pH;
dissolved oxygen;
temperature;
flow conditions;
pipe material.

General Corrosion

General corrosion affects a relatively broad surface area.

Over time, it can reduce wall thickness and structural strength.

Pitting Corrosion

Pitting is localized corrosion that creates small but potentially deep areas of metal loss.

Pitting can be dangerous because severe wall loss may exist even when most of the surrounding surface looks acceptable.

Galvanic Corrosion

Galvanic corrosion can occur when dissimilar metals are electrically connected in a conductive environment.

The more active metal may corrode faster.

Good material selection and proper isolation can reduce this risk.

Corrosion Under Deposits

Deposits can create localized conditions that increase corrosion beneath them.

Examples include:

scale;
solids;
biological deposits;
chemical residue.

Corrosion Warning Signs

Operators should report conditions such as:

rust streaks;
flaking metal;
deep pitting;
bulging;
weeping;
pin-hole leaks;
coating failure;
loss of section at bolts or supports.

Surface Rust Versus Significant Metal Loss

Light surface rust does not automatically mean immediate structural failure.

Greater concern exists when corrosion causes:

deep pitting;
wall thinning;
leakage;
loss of support;
reduced bolt or fastener section.

Coatings

Protective coatings help isolate metal or concrete from corrosive environments.

Coating maintenance may include:

inspection;
surface preparation;
spot repair;
recoating.

Coating Failure

Signs of coating failure include:

blistering;
peeling;
cracking;
rust beneath coating;
loss of adhesion.

Surface Preparation Matters

A new coating applied over poorly prepared surfaces may fail quickly.

Good coating work generally requires:

removal of loose material;
clean surface;
appropriate dryness;
compatible coating system.

Pipe Leaks

Leaks may occur at:

pipe walls;
flanges;
threaded joints;
valves;
gaskets;
expansion joints;
mechanical couplings.

Leak Severity

Leak severity depends on:

fluid;
pressure;
flow rate;
location;
equipment affected;
safety impact;
process impact.

Small Leaks Can Grow

A small leak can indicate:

gasket deterioration;
corrosion;
cracking;
movement;
pressure cycling.

It should be documented and evaluated rather than ignored.

Temporary Leak Repairs

Temporary leak repairs may sometimes be used until permanent work can be completed.

Temporary repairs should be:

appropriate for pressure and service;
authorized;
documented;
inspected;
tracked until permanent repair.

Do Not Treat Every Clamp as Permanent

A repair clamp may be suitable as a permanent engineered repair in some applications, but in other situations it may only be temporary.

The intended repair status should be clearly documented.

Flange Maintenance

Flanged joints should be checked for:

leakage;
corrosion;
damaged bolts;
gasket failure;
misalignment.

Flange Bolt Condition

Severely corroded flange bolts can reduce joint reliability.

Replacement should be planned before bolts lose significant section or become unsafe to remove.

Gaskets

Gasket failure can result from:

age;
incorrect material;
poor installation;
misalignment;
excessive pressure;
chemical attack.

Threaded Connections

Threaded connections should be inspected for:

leakage;
corrosion;
cracked fittings;
looseness.

Pipe Supports

Pipe supports carry pipe weight and control movement.

Support systems may include:

hangers;
brackets;
anchors;
guides;
stands.

Failed Pipe Supports

Signs include:

sagging;
broken hangers;
loose bolts;
unexpected movement;
pipe resting on unrelated equipment;
misaligned flanges.

Why Supports Matter

Poor support can transfer loads into:

pumps;
valves;
flanges;
equipment nozzles.

This can contribute to leakage, alignment problems, and structural damage.

Pipe Strain

Pipe strain occurs when connected piping applies excessive force to equipment.

Possible causes include:

poor support;
misalignment;
thermal movement;
settlement;
forced installation.

Thermal Expansion

Temperature changes can cause piping to expand and contract.

Systems may use:

expansion joints;
loops;
anchors;
guides.

Expansion Joint Inspection

Expansion joints should be inspected for:

cracking;
leakage;
distortion;
excessive movement;
corrosion.

Pipe Vibration

Pipe vibration may result from:

pump vibration;
hydraulic transients;
unstable flow;
poor supports;
check-valve slam.

Repeated movement can fatigue piping and supports.

Water Hammer Damage

Hydraulic transients can contribute to:

pipe movement;
joint damage;
support damage;
valve damage;
leaks.

Valve Maintenance

Valve maintenance may include:

inspection;
exercising;
lubrication where applicable;
packing adjustment;
actuator maintenance;
seat or seal repair.

Valve Exercising

Valves that remain in one position for long periods may become difficult to operate.

Periodic exercising can help identify:

sticking;
stem problems;
actuator problems;
incorrect position records.

Exercise Valves Carefully

Before moving a normally fixed valve, consider:

process impact;
pressure changes;
flow changes;
risk of water hammer;
whether the valve can be returned to its original position.

Valve Stem Maintenance

Exposed stems should be inspected for:

corrosion;
damage;
thread condition;
lubrication requirements.

Valve Packing

Valve packing controls leakage around the stem.

Excessive leakage may indicate:

worn packing;
loose packing gland;
damaged stem.

Do Not Overtighten Valve Packing

Excessive tightening can:

increase operating torque;
damage packing;
damage the stem.

Valve Seat Leakage

A closed valve may still pass liquid internally.

Possible signs include:

pressure downstream;
continued flow;
unexpected tank filling;
inability to isolate equipment.

Check-Valve Maintenance

Check valves should be evaluated for:

reverse leakage;
slam;
sticking;
wear;
obstruction.

Actuator Maintenance

Actuated valves may require maintenance of:

electric motor;
gearbox;
limit switches;
torque switches;
air supply;
hydraulic system;
control signals.

Structural Maintenance

Water and wastewater facilities contain structures such as:

concrete basins;
tanks;
walkways;
platforms;
stairs;
handrails;
steel supports;
buildings.

Concrete Deterioration

Concrete problems may include:

cracking;
spalling;
surface erosion;
chemical attack;
exposed reinforcing steel;
leakage through cracks or joints.

Concrete Cracks

Cracks should be evaluated for:

width;
length;
location;
change over time;
water leakage;
movement.

Not Every Concrete Crack Has the Same Meaning

Some cracks may be minor shrinkage cracks, while others may indicate:

structural movement;
settlement;
chemical deterioration;
reinforcement corrosion.

Significant or changing cracks should be evaluated by qualified personnel.

Spalling

Spalling is breaking or flaking of the concrete surface.

Possible causes include:

reinforcing-steel corrosion;
freeze-thaw damage;
chemical attack;
impact.

Exposed Reinforcing Steel

Exposed reinforcing steel can corrode and expand, causing additional concrete damage.

This condition should be evaluated and repaired.

Hydrogen Sulfide and Concrete

Wastewater environments containing hydrogen sulfide can contribute to severe corrosion of concrete and metal, especially in enclosed or poorly ventilated areas.

Signs may include:

softened concrete surface;
surface loss;
exposed aggregate;
corroded metal components.

Steel Structures

Steel structures should be inspected for:

corrosion;
section loss;
loose connections;
cracks;
coating failure;
deformation.

Handrails and Guardrails

Handrails and guardrails should be:

secure;
structurally sound;
free of severe corrosion;
properly anchored.

Stairs and Walkways

Inspect for:

corrosion;
loose grating;
damaged steps;
missing fasteners;
slip hazards;
poor drainage.

Tank Inspection

Tank inspection may include:

leaks;
corrosion;
coating condition;
foundation condition;
roof condition;
access hatches;
vents;
ladders;
overflow structures.

Foundation Settlement

Settlement can affect:

tanks;
buildings;
piping;
equipment alignment.

Possible signs include:

new cracks;
misaligned piping;
doors that no longer close correctly;
uneven equipment bases.

Drainage Around Structures

Poor drainage can contribute to:

foundation problems;
corrosion;
water intrusion;
freeze damage;
slip hazards.

Roof and Building Leaks

Building leaks can damage:

electrical equipment;
instrumentation;
insulation;
structural components.

Housekeeping Supports Structural Inspection

Clean, accessible areas make it easier to identify:

new leaks;
cracks;
corrosion;
movement;
damaged supports.

Inspection Records

Useful structural and piping records may include:

asset or location;
date;
condition;
photographs where useful;
measurements;
work order number;
repair completed.

Measure Changes Over Time

When deterioration is being monitored, useful measurements may include:

crack width;
corrosion depth;
wall thickness;
leak rate;
movement;
settlement.

Wall-Thickness Measurement

Specialized inspection methods such as ultrasonic thickness testing can help evaluate metal loss without cutting into the pipe.

Testing should be performed by trained personnel using appropriate equipment.

Do Not Rely Only on External Appearance

A pipe that looks acceptable externally may still have internal corrosion or erosion.

Inspection methods should match the known failure risks of the asset.

Repair Prioritization

Repair priority should consider:

safety;
leak severity;
remaining wall or structural strength;
process importance;
likelihood of rapid deterioration;
availability of redundancy.

Conditions Requiring Rapid Response

Examples may include:

rapidly growing leak;
severe wall loss;
unstable support;
major structural crack;
damaged handrail over an open basin;
pipe movement under pressure;
loss of equipment isolation capability.

Safe Inspection

Piping and structural inspections may involve hazards such as:

pressurized systems;
chemicals;
confined spaces;
falls;
traffic;
sharp corroded surfaces.

Inspection methods must follow facility safety procedures.

Never Assume a Closed Valve Means Zero Pressure

Before maintenance begins, verify isolation and safely relieve stored pressure.

A leaking isolation valve can leave equipment or piping pressurized.

Lockout/Tagout and Process Isolation

Maintenance may require control of:

electrical energy;
hydraulic pressure;
pneumatic pressure;
chemical flow;
gravity flow.

Confined Spaces

Internal inspection of tanks, vaults, pits, and some structures may involve confined-space requirements.

Do not enter unless the required evaluation, permit, atmospheric testing, and protective procedures are in place.

Common Piping Maintenance Mistakes

Ignoring small leaks until they become major failures.
Ignoring corroded supports and fasteners.
Forcing misaligned piping into place.
Assuming external appearance reveals all internal corrosion.
Leaving temporary repairs undocumented.
Ignoring pipe movement and vibration.
Failing to investigate repeated flange or gasket leaks.

Common Valve Maintenance Mistakes

Forcing a stuck valve.
Operating a large valve too rapidly.
Failing to exercise critical isolation valves.
Ignoring valve packing leakage.
Assuming a closed valve provides perfect isolation.
Ignoring actuator alarms or torque trips.
Failing to restore the correct valve lineup after maintenance.

Common Structural Maintenance Mistakes

Ignoring cracks because they appear small.
Ignoring corrosion at stairs, handrails, and platforms.
Painting over active corrosion without proper preparation.
Ignoring water intrusion and poor drainage.
Failing to track crack growth or settlement.
Delaying repair of damaged safety barriers.

A Practical Piping Inspection Sequence

Identify the piping system and service.
Inspect for leaks and corrosion.
Inspect flanges, joints, and fittings.
Check pipe supports and anchors.
Look for vibration or unexpected movement.
Inspect coatings and insulation where visible.
Check for evidence of settlement or pipe strain.
Document abnormal conditions.
Create a work order and assign priority based on risk.

A Practical Valve Inspection Sequence

Confirm valve identification and normal position.
Inspect for external leakage.
Check stem and actuator condition.
Review position indication.
Check for unusual operating force or torque alarms.
Exercise the valve according to approved procedures where required.
Verify that the valve returns to the required position.
Document condition and maintenance needs.

A Practical Structural Inspection Sequence

Inspect concrete for cracks, spalling, erosion, and leakage.
Inspect steel for corrosion and section loss.
Check handrails, ladders, stairs, and grating.
Inspect supports, anchors, and fasteners.
Look for settlement or movement.
Inspect coatings and protective systems.
Check drainage and water intrusion.
Measure or photograph significant defects where useful.
Escalate structural concerns to qualified personnel.

What to Remember for the Exam

Piping maintenance focuses on pressure integrity, flow capacity, joints, supports, corrosion protection, and isolation capability.
External and internal corrosion can reduce pipe wall thickness and structural strength.
Pitting is localized corrosion that can create deep wall loss in a small area.
Galvanic corrosion can occur when dissimilar metals are electrically connected in a conductive environment.
Protective coatings help isolate surfaces from corrosive environments.
Small leaks should be evaluated because they can indicate corrosion, gasket failure, cracking, or movement.
Temporary repairs should be documented and tracked until permanent disposition is determined.
Pipe supports prevent excessive movement and reduce loads transferred to equipment.
Pipe strain can contribute to equipment misalignment and seal or flange leakage.
Thermal expansion must be accommodated by appropriate piping design features.
Valve exercising can identify sticking and maintain operability of infrequently used valves.
Do not force a stuck valve or operate large valves unnecessarily fast.
A closed valve may still leak internally and should not be assumed to provide perfect isolation.
Concrete deterioration can include cracking, spalling, erosion, chemical attack, and exposed reinforcement.
Spalling is breaking or flaking of the concrete surface.
Hydrogen sulfide environments can severely damage wastewater concrete and metal components.
Steel stairs, handrails, platforms, and supports should be inspected for corrosion and structural deterioration.
Changes in crack width, wall thickness, settlement, or leakage should be tracked over time.
Repair priority should consider safety, structural condition, process importance, and likelihood of further deterioration.
Stored pressure must be safely isolated and relieved before piping or valve maintenance.