Sewer shafts often hidden beneath inconspicuous manhole covers are essential to the smooth operation of urban sewage systems. They connect the surface with the underground sewer network, provide critical access points for inspection and maintenance, and ensure the reliable conveyance of wastewater to treatment plants. In a city like Cologne, for example, around 58,000 sewer manholes are part of a 2,377 km-long sewer network.
These manholes serve multiple roles: ventilating the system, allowing maintenance access, and compensating for elevation differences. Their structural integrity and watertightness are crucial not only for the safe transport of wastewater but also for preventing contamination of surrounding soil and groundwater. Experts therefore stress that manholes must be properly maintained as “an essential part of urban infrastructure.”
The central role of sewer manholes in the wastewater network
Manholes act as the hubs of municipal wastewater management. They link sewer pipes to one another and to the surface. House connections typically feed into manholes, allowing access to the system without extensive excavation. Manholes also ventilate the sewer system, preventing gas buildup, and provide entry points for sampling and flow measurement. In short, without fully functioning shafts, a sewer network cannot operate effectively.
They serve as the “access doors” of the system essential for inspection, cleaning, and repair. Their condition is thus critical: watertightness is essential for both groundwater protection and public health. When shafts fail, the resulting problems can affect the entire wastewater system, all the way to the treatment plant.
Consequences of neglected or defective shafts
Neglecting the maintenance of sewer shafts can lead to significant technical, economic, and environmental problems. Historically, many cities focused on rehabilitating main pipes while giving less attention to manholes. The resulting issues often develop gradually: cracks, leaky joints, and corrosion can lead to groundwater entering the system (infiltration) or sewage leaking out (exfiltration).
Infiltrating groundwater burdens the sewer system and wastewater treatment plants, especially during rainfall events. A dramatic example occurred in Napa Valley, USA, where heavy rains caused the volume of wastewater to surge from 6 to almost 60 million gallons per day, mainly due to infiltration via leaky shafts.
The tenfold increase overwhelmed the treatment plant, escalated operating costs, and forced the facility to process what was essentially clean groundwater and rainwater.
In one U.S. region, infiltration-related costs are estimated at $300–400 million annually. Cities are faced with a stark choice: invest in fixing leaks or spend even more expanding plant capacity. A cost comparison in Minnesota showed that infiltration mitigation would cost $150 million, while plant expansion to handle peak flows would require nearly $1 billion. The economic benefits of proactive shaft renovation are undeniable.
In Germany, the problem is similarly acute. Experts estimate that 10–20% of the country’s 13.5 million sewer shafts are in urgent need of repair. Infiltrating groundwater raises treatment costs, while exfiltrating sewage endangers soil and water quality, potentially triggering regulatory penalties and clean-up expenses. Moreover, infrastructure and public safety are at risk: leaking shafts can undermine roads, leading to potholes or even sinkholes, and loose manhole covers pose serious traffic hazards. As one renovation company succinctly puts it: neglected manholes often lead to major damage and costly repairs.
In summary, defective shafts negatively affect public finances, infrastructure resilience, the environment, and safety. These often-overlooked “basement doors” of the city can become major liabilities, from rising energy and treatment costs to environmental fines and expensive road repairs.
Renovation needs and market potential: A global outlook
Given these consequences, it’s no surprise the global market for shaft renovation is experiencing strong growth. Cities and municipalities are increasingly realizing that preventive maintenance is far more economical than emergency repairs. The aging of sewer networks worldwide is fueling demand for rehabilitation technologies. Industry experts describe the global trenchless sewer and shaft rehabilitation market as dynamic and growing, driven by a focus on sustainable infrastructure and modernisation. By the mid- 2020s, this market is estimated to be worth around US$5 billion annually and rising. Technological innovations, such as robotic milling, modern coating systems, AI-driven inspections, and advanced resins, are accelerating this growth.
Locally, the demand is also significant. In Germany alone, around 1 million of the estimated 10 million sewer manholes require rehabilitation, at an expected cost of €3 billion. The U.S. has approximately 20 million sewer manholes, many of them decades old and in need of repair. Even in rapidly developing regions like Asia, demand for high-quality manhole systems is growing, as dense sewer networks are a prerequisite for sustainable urban development. Worldwide, governments are investing heavily in water and wastewater infrastructure through national programs and urban growth initiatives. Sector experts report a surge in funding and project activity for manhole and sewer rehabilitation in recent years. The conclusion is clear: manhole rehabilitation is a booming sector offering major opportunities for cities, contractors, and materials suppliers.
Innovative solution providers: Bodenbender Group and IPA Bauchemie
Delivering high-quality shaft renovation requires deep technical expertise and reliable products. Two German companies that have earned strong reputations in this space are Bodenbender GmbH, a specialist in sewer and pipe renovation products, and IPA Bauchemische Produkte GmbH, an expert in construction chemicals and coating systems.
Both family-run firms have collaborated closely for years, and in autumn 2023, they deepened their partnership by integrating IPA into the Bodenbender Group. The aim, according to Managing Director Jonas Bodenbender, is “to set quality standards in shaft renovation with our products.”
This alliance brings together practical renovation experience and chemical expertise, enabling the companies to respond flexibly to real-world challenges. One standout result of the collaboration is IPA Polyschicht®, a specially developed coating resin that hardens even under water, withstands temperatures up to 130°C, and can be made electrostatically conductive. Ideal for harsh environments like industrial separators or biogas plants, this material meets the most demanding conditions. IPA also brings a portfolio of certified products for wastewater handling (WHG areas, dome shafts, etc.) and benefits from access to new markets through Bodenbender’s distribution network.
Their joint development, “SchachtHero,” is a comprehensive all-in-one shaft renovation system. It covers every stage of the process—from waterproofing and structural repair to final corrosion protection with harmonised products that work in sync.
The three functional steps of the SchachtHero System:
1. Sealing against water infiltration: Leaks are sealed using swellable synthetic resins like IPAPUR, which expands 10–20 times on contact with water, or IPANEX rapid-setting mortars, which harden even in running water to immediately stop inflow.
2. Reprofiling the building fabric: Damaged concrete or masonry is repaired using high-strength mortars like IPA Unimörtel, available in multiple variants for different grain sizes and site conditions. Unimörtel Rapid offers fast curing for urgent jobs, and mineral grouting mortars fill annular gaps and voids to restore structural stability.
3. Protective coating for long-term durability: Finally, long-lasting coatings such as IPA Polyschicht® provide robust chemical and thermal resistance (pH 0–14), even on damp substrates. Additional options include Elastikschlämme for crack bridging and Mörtel Kanal pH+ for acid protection in corrosive environments.
This coordinated system significantly extends the life of shafts, reduces infiltration, and restores structural integrity, cutting operating costs and environmental risks for cities.
Conclusion: Economic and environmental benefits of sustainable shaft renovation
Sewer shaft rehabilitation is far from a niche concern it is central to the sustainability and efficiency of urban infrastructure. Intact shafts reduce infiltration, protect groundwater, prevent road damage, and minimise energy and treatment costs. Investing in renovation is a proactive strategy that saves money and enhances system reliability over the long term.
Modern trenchless methods and advanced materials such as those developed by the Bodenbender Group also reduce surface disruption, benefitting traffic and urban life. Moreover, this growing sector supports local economies by creating jobs for contractors, tradespeople, and material suppliers.
In summary, manhole rehabilitation is a smart investment in infrastructure resilience. With the right products and partners like Bodenbender and IPA, cities can transform problematic shafts into high-performance assets that are ready for the future.
