Pipe Rehabilitation Glossary – Common Terms and What They Mean

Pipe Rehabilitation Glossary – Common Terms and What They Mean

In plumbing and pipe rehabilitation, many terms are used by clients, technicians, and companies — not always with the same meaning.

On this page, we gather the most common terms and explain, in a simple and practical way, what they actually mean and how they apply in real situations.

Pipe rehabilitation

A general term used to describe interventions that extend the lifespan of an existing pipe without fully replacing it.

In practice, it may refer to:

• internal epoxy coating

• rehabilitation with felt or fiberglass liner (CIPP)

The meaning depends on the technology used.

Pipe repair

A common expression used for any type of intervention in a damaged pipe.

It may include:

• localized repairs

• replacement of small sections

• or internal solutions without opening walls

It does not always mean full pipe replacement.

Repair pipes without breaking walls

Refers to techniques that allow intervention from inside the pipe, avoiding invasive construction work.

Includes:

• epoxy

• CIPP

• localized repairs

Feasibility depends on the condition of the pipe.

Internal epoxy coating

Application of a continuous layer inside the pipe to improve watertightness and protect the internal surface.

Often associated with terms such as:

• “pipe painting”

• “pipe sealing”

When to use

• structurally stable pipe

• cracks or micro-leaks

• deteriorated joints

• presence of multiple lateral connections (adapts well to entries)

• internal wear or irregularities

Widely used in wastewater and rainwater systems.

Felt or fiberglass liner (CIPP)

A rehabilitation system where a new pipe is created inside the existing one.

Also known as:

• “pipe inside pipe”

• CIPP (Cured In Place Pipe)

When to use

• loss of pipe material

• extensive cracking

• deformation

• advanced deterioration

Pipe inside pipe

A common expression used to describe CIPP rehabilitation.

In practice:

• a new continuous pipe is created

• inside the existing pipe

• without excavation or demolition

Felt liner

A type of liner used in internal pipe rehabilitation, usually impregnated with resin and cured inside the pipe.

It is an alternative to fiberglass liner.

When to use

• smaller diameters or simple geometries

• situations where high structural strength is not required

• limited access conditions or need for flexible material

Technical note

Compared to fiberglass liners, it has lower structural capacity and is mainly used for sealing and reinforcement rather than full structural rehabilitation.

Packer / Packers

Inflatable equipment used to perform localized repairs inside pipes.

It works like a technical “balloon” that positions and presses materials (such as resins or short liners) against the pipe wall.

When to use

• localized repairs (cracks, open joints)

• specific leakage points

• situations where full-length rehabilitation is not required

Technical note

Allows fast and precise interventions.

In older systems, patch repairs may solve one issue but others can appear shortly after, making a more comprehensive approach more suitable.

Resin

Material used in pipe rehabilitation processes, responsible for forming the new internal layer or structure after curing.

Used in:

• epoxy coatings

• liners (felt or fiberglass)

• localized repairs with packers

When to use

The choice of resin depends on:

• type of intervention

• pipe condition

• application method

• environment (wastewater, rainwater, etc.)

Technical note

The quality of the resin and correct application directly affect durability and final performance.

Curing (resin curing)

Process through which the resin transitions from liquid to solid, forming a resistant structure inside the pipe.

Curing methods include:

• time (natural curing)

• heat

• UV / LED light

When relevant

• in all resin-based processes

• in defining execution time

• in ensuring final quality

Technical note

Proper curing ensures:

• correct adhesion

• mechanical strength

• durability

Leaks in pipes

Water loss or infiltration caused by pipe defects.

Can result from:

• cracks

• open joints

• material wear

• faulty connections

Not always directly visible.

Infiltration

Water entering or escaping through non-watertight sections of a pipe.

Often associated with:

• damp walls

• stains

• odors

• structural degradation

Stack (vertical pipe / riser)

Vertical pipe in a building that carries wastewater or rainwater.

A critical area, especially in older buildings.

• epoxy coating of stacks

• rehabilitation with felt or fiberglass liner (CIPP)

Branch pipe (lateral)

Connection between fixtures (toilet, sink, etc.) and the main stack.

May present:

• irregular connections

• deposits

• small cracks

Wastewater

Water from domestic use (toilets, kitchens, sinks).

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Rainwater

Water from rainfall conducted through dedicated systems (drains, gutters, external pipes).

Trenchless rehabilitation

Term used to describe interventions carried out without opening walls or floors.

Includes:

• epoxy

• CIPP

Not all situations allow fully trenchless solutions.

CCTV pipe inspection

Diagnostic method that allows visualization of the pipe interior using a camera.

Used to:

• identify problems

• assess pipe condition

• define the appropriate solution

It is the starting point for any technical decision.

DN (Nominal Diameter)

DN (nominal diameter) indicates the approximate internal diameter of a pipe.

Common examples:

• DN50, DN75, DN90, DN110 (domestic use)

• DN125, DN160, DN200 (larger systems)

• DN300+ (main networks and infrastructure)

Application in rehabilitation solutions

Different technologies cover different diameter ranges:

Epoxy coating (brush system)

• approx. DN32 to DN300

• commonly used in domestic stacks and branches

• adaptable to complex geometries

CIPP rehabilitation

• approx. DN70 to DN1600+

• used from domestic systems to industrial and municipal networks

• more suitable for medium and large diameters

Technical note

The choice depends not only on diameter, but also on pipe condition, access, and type of network.

Offset / pipe misalignment

Refers to a level difference between two pipe sections at a joint, where one is not aligned with the other.

Common in:

• old clay pipes

• ground settlement

• irregular installations

When relevant

• may cause debris accumulation

• increases risk of blockages

• may indicate structural instability

Technical note

Epoxy coating does not correct misalignment.
CIPP can accommodate slight offsets, but does not correct the original alignment.

Severe cases may require structural intervention or replacement.

Flexible liner

A type of liner that easily adapts to the pipe geometry.

Can be made of:

• felt

• flexible fiberglass

When to use

• pipes with curves or slight alignment variations

• systems with multiple connections

• situations where adaptability is important

Technical note

Flexibility helps installation but must match the objective (sealing vs structural rehabilitation).

Pre-impregnated liner

A liner supplied with resin already incorporated at the factory, ready for installation.

Used in CIPP systems, especially with UV/LED curing.

When to use

• projects requiring high quality control

• faster and more predictable installations

• situations where reducing on-site variability is important

Technical note

• ensures uniform resin distribution

• reduces installation errors

• improves curing control

Flexible vs rigid liner (additional note)

Simplified:

• more flexible liners → better adaptation to geometry

• more rigid liners (e.g. structured fiberglass) → higher structural capacity

The choice depends on pipe condition and intervention goal.

Solution selection – technical suitability

In pipe rehabilitation, there is no universally “better” or “worse” solution.

There is only the solution that is more appropriate — or not applicable — to the actual condition of the pipe.

A correct intervention depends on:

• structural condition

• material (clay, PVC, etc.)

• extent of damage

• available access

• type of network

The goal is always to match the technology to the real problem — not the other way around.

Quick selection guide (general orientation)

Light cracks / micro-leaks / deteriorated joints
→ Internal epoxy coating

Structurally stable pipe with infiltration
→ Epoxy coating

Multiple irregular lateral connections
→ Epoxy (better adaptation)

Localized issue
→ Packer repair

Extensive cracks / multiple critical points
→ Evaluation for broader solution

Material loss / advanced degradation
→ CIPP

Deformation / risk of collapse
→ CIPP

Old clay pipes with recurring issues
→ Prefer full or integral approach

Final note

The correct solution should always be based on a proper diagnosis.

In many cases, the decision is not simply “epoxy or CIPP”, but:

• localized repair

• partial rehabilitation

• or full rehabilitation

Each situation requires its own approach.