Rehabilitate or replace building stacks? What to assess before deciding
When leaks, unpleasant odours or recurring blockages appear in a building, the first reaction is often to consider replacing the drainage stacks. In many cases, this decision is made based on symptoms rather than on the actual internal condition of the pipework.
But is replacement always necessary? Or are there technical alternatives that allow the problem to be solved, extend the service life of the stacks and avoid major disruptive works?
Before committing to an expensive and highly invasive intervention, there are several key aspects that should be carefully assessed.
Why drainage stacks fail in older buildings
Most buildings experiencing drainage stack problems are 30, 40 or more years old. Wastewater and rainwater systems were designed with a limited service life and built using materials that are now considered outdated, such as clay (vitrified clay), cast iron or early-generation PVC.
Over time, it is common to observe:
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degraded or misaligned joints
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cracks and micro-fractures
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intermittent leaks
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accumulation of deposits
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root intrusion
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gradual loss of watertightness
Many of these issues develop slowly and only become visible once damage has already occurred to walls, ceilings or neighbouring units.
When replacement of stacks is truly necessary
Full replacement of drainage stacks is unavoidable in specific situations, namely when there is:
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structural collapse of the pipe
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significant crushing or deformation
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complete loss of internal section
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lack of continuity along the pipe
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extreme degradation that prevents any internal repair
In such cases, internal rehabilitation is no longer technically feasible and replacement becomes the only viable solution.
Why many stack replacements are carried out unnecessarily
In practice, many stack replacements are decided without any internal inspection. The decision is often based on external symptoms, isolated incidents or assumptions.
It is common to find situations where:
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the pipework is heavily soiled and has not been properly assessed
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defects are localised rather than structural
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the issue lies in a specific joint rather than the entire stack
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the pipe retains sufficient structural integrity for rehabilitation
In these cases, proceeding directly to replacement results in higher costs, more disruption and more extensive works than necessary.
What should be assessed before replacing drainage stacks
Before making any decision, it is essential to understand the actual internal condition of the infrastructure. This can only be achieved through a CCTV inspection.
A proper technical assessment should answer key questions such as:
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What is the real extent of the defects?
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Are there ruptures, or only cracks and open joints?
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Does the pipe maintain structural stability?
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Is internal rehabilitation technically viable?
Without these answers, any decision carries technical and financial risk.
Drainage stack rehabilitation: when it is possible
Internal rehabilitation of drainage stacks restores watertightness and functionality through processes such as cleaning, surface preparation and the application of technical resins inside the pipe.
When carried out at the right time, rehabilitation:
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eliminates leaks and loss of watertightness
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avoids demolition and invasive works
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significantly reduces intervention time
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extends the service life of drainage stacks by up to 30 additional years
This solution is particularly effective when the pipe maintains structural continuity despite localised degradation.
Replacement vs rehabilitation: a direct comparison
Stack replacement
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Highly invasive works across multiple units
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Noise, dust and demolition
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Long execution periods
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High costs
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Major disruption to occupants
Stack rehabilitation
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Internal intervention without demolition
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Faster execution
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Minimal impact on the building
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Controlled costs
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Extended service life of the pipework
Every case is different, but the decision should be technical, not automatic.
Conclusion: without CCTV inspection, the decision is always a risk
Replacing drainage stacks may be necessary — but it should never be the first step without a proper diagnosis. In many buildings, CCTV inspection shows that rehabilitation is fully viable, avoiding extensive works, high costs and prolonged disruption.
CCTV inspection is the starting point for any responsible decision. Only by seeing inside the stacks can owners, building managers and engineers choose between rehabilitation and replacement with confidence, technical accuracy and cost control.
Acting at the right time preserves the building, saves money and prevents unnecessary disruption.
