Sewer Stack Rehabilitation with Internal Epoxy Coating

Internal epoxy coating for sewer stacks – an effective solution for pipes with multiple branch connections

Sewer pipes in buildings, particularly vertical stacks, are subject to natural wear over time. Cracks, deteriorated joints, small leaks and accumulated deposits are common problems, especially in buildings that have been in service for several decades.

Traditionally, the solution for these problems involved replacing the damaged pipes, which often meant opening walls, floors or service shafts, causing disruption for residents and significant repair costs.

Today, modern trenchless technologies allow the internal rehabilitation of pipes without invasive construction work. Among these solutions, internal epoxy coating has proven particularly suitable for sewer stacks with multiple branch connections.

Common problems in building sewer stacks

In many residential buildings, the main vertical stack receives several branch connections from each floor. In typical configurations there are two branch connections per floor, corresponding to bathrooms, kitchens or other sanitary installations.

This results in a pipe configuration that includes:

• multiple branch entries along the stack

• short distances between connections

• bends and direction changes

• sections of pipe that may have been replaced over time with different materials

Over the years, this type of network can develop problems such as:

• cracks in the pipe wall

• deteriorated joints

• leaks affecting walls or service shafts

• accumulation of deposits near branch connections

Before planning any rehabilitation work, it is essential to carry out a CCTV pipe inspection, which allows direct observation of the pipe interior and accurate identification of existing defects.

Internal epoxy pipe coating

Internal epoxy coating consists of applying a specially formulated resin to the inner surface of the pipe, creating a continuous protective layer that seals cracks, joints and deteriorated areas.

The process typically includes several steps:

1. mechanical cleaning of the pipe

2. removal of grease and deposits

3. preparation of the internal surface

4. controlled application of epoxy resin

After curing, the resin forms a smooth and resistant internal coating that restores the tightness of the pipe and improves flow conditions.

Key advantages include:

• no demolition work required

• shorter intervention time

• preservation of the existing pipe structure

• improved leak sealing and durability

Application methods: brushing and spray coating

Depending on the geometry of the pipe and the site conditions, epoxy coating can be applied using different techniques.

Brushing application

Brushing allows precise control of the resin distribution and is particularly suitable for vertical stacks with multiple branch entries. This method allows technicians to carefully reinforce and seal the areas around the branch connections.

Spray application

In certain situations, spray application allows a more uniform distribution of the epoxy coating along the pipe surface, ensuring a consistent protective layer.

The choice of application method depends on the configuration of the pipe and the nature of the defects identified during inspection.

Advantages in sewer stacks with many branch connections

In vertical sewer stacks where numerous branch pipes connect to the main column, internal epoxy coating offers an important advantage: it adapts to the existing geometry of the pipe and its connections.

Instead of inserting a rigid liner that creates a completely new pipe inside the original one, epoxy coating follows the internal contours of the system, allowing technicians to:

• seal the connection zones between the stack and the branch pipes

• reinforce areas affected by cracks or minor structural damage

• maintain the original geometry of the branch connections

This makes epoxy coating particularly well suited for complex building drainage systems with multiple connections along the vertical stack.

Other pipe rehabilitation technologies

Several trenchless rehabilitation technologies exist for pipe repair, including structural lining systems such as CIPP (Cured-In-Place Pipe).

CIPP is widely used in underground drainage networks and in long pipe sections with relatively few lateral connections, where it can create a new structural pipe within the existing one.

The most appropriate rehabilitation method depends on several factors, including:

• the condition of the pipe

• the configuration of the drainage network

• the number of branch connections

• accessibility of the system

For this reason, a technical evaluation is always necessary before selecting the most suitable rehabilitation solution.

The importance of CCTV pipe inspection

CCTV pipe inspection is an essential diagnostic tool for evaluating the condition of drainage systems. Using high-resolution cameras, technicians can identify:

• cracks and fractures

• open or displaced joints

• root intrusion

• deposits or blockages

• defects around branch connections

Based on this analysis, it becomes possible to determine the most effective rehabilitation strategy, ensuring that the chosen method is appropriate for the specific configuration of the pipe system.

Conclusion

Modern pipe rehabilitation technologies allow many drainage problems to be resolved without the need for disruptive construction work.

In sewer stacks with multiple branch connections, internal epoxy coating provides a flexible and adaptable solution, capable of sealing leaks and restoring pipe integrity while preserving the existing network layout.

However, every case should be evaluated individually, and CCTV inspection remains the essential first step in selecting the most appropriate technical solution.