Aging joint seals in plastic pipes: why infiltration develops over time

Old joint seals in plastic pipes: what we repeatedly observe during inspections

During CCTV inspections carried out by REVIPOX, one recurring pattern is frequently observed in plastic pipe systems (particularly PVC):
the joints appear visually intact, yet they no longer provide functional watertightness.

This phenomenon is common in pipe networks that have been in service for several years and explains many infiltration issues that are difficult to justify at first glance.

Why joint seals in PVC pipes degrade over time

Glued joints in plastic pipes rely on an adhesive material that, at the time of installation, ensures bonding and watertightness.
Over the years, this adhesive is subject to several degradation mechanisms:

• Natural ageing of the adhesive, with loss of elasticity;

• Micro-movements of the pipework, caused by thermal variations, vibrations, or settlement;

• Prolonged exposure to moisture, particularly in wastewater and rainwater systems;

• Repeated hydraulic loading, especially during periods of heavy rainfall;

• Shrinkage or retraction of the glue, creating microscopic discontinuities.

The result is rarely an obvious rupture, but rather a progressive loss of watertightness at the joint.

The misleading appearance of joints during inspections

One of the most important aspects to clarify for clients is the following:

A joint may appear visually closed on camera and still allow infiltration.

During CCTV inspections, we often observe:

• joints that remain structurally intact;

• no visible linear cracks;

• yet glue extrusion, irregular sealing beads, or runoff marks.

In many cases, the behaviour of water — persistent sheen, adhered flow, or localized trickling — is more indicative of a problem than the geometry of the joint itself.

Why these infiltrations often go unnoticed for years

In vertical stacks, infiltrated water tends to:

• run along the exterior of the pipe;

• enter common collectors or drainage boxes;

• cause no immediate visible damage inside dwellings.

It is usually only when there is a horizontal section, a sensitive wall, or a period of prolonged rainfall that the problem becomes clearly noticeable.

Degraded joint seals are not a manufacturing defect

It is important to distinguish between:

• an isolated defect
  and

• homogeneous ageing of the system.

In most cases we analyse, the issue is not an isolated installation error but a predictable ageing process occurring after years of service.

For this reason, purely localized repairs do not always provide a durable solution.

How REVIPOX approaches these situations

Our approach is based on three key principles:

1. Rigorous diagnosis, using CCTV inspection with functional analysis, not merely visual observation;

2. Prudent technical language, clearly separating what is observed from what is interpreted;

3. Proportionate solutions, which may be:

   • corrective (when active rupture is present);

   • preventive (when the risk of infiltration is progressive).

In many cases, internal sealing with epoxy resin allows the watertightness of the joints to be restored and significantly extends the service life of the pipework, without the need for full replacement.

Conclusion

Old joint seals in plastic pipes rarely fail suddenly.
They fail gradually and silently, until external signs finally become evident.

Understanding this mechanism is essential to:

• correctly interpret inspection results;

• avoid ineffective spot repairs;

• make informed and durable technical decisions.

At REVIPOX, we believe that clearly explaining the problem is just as important as solving it.