Concrete manholes may seem simple, but they fail in predictable ways that cost cities millions each year. Understanding the top failure modes is the first step toward sustainable, long-term solutions.
Key Failure Modes of Concrete Manholes
Corrosion
Hydrogen sulfide gases, acidic conditions, salt (in coastal or de-icing zones) all contribute to corrosion of concrete. Over time, these acids eat away at the concrete, weaken joints, and reduce structural integrity, meaning more frequent repairs.
Freeze–Thaw Cracking
In colder climates, water can penetrate concrete, freeze, expand, and cause cracks. Repeated cycles worsen the fissures. Cracked joints allow infiltration/inflow (I&I), soil movement, and eventual structural compromise.
Root Intrusion
Trees and shrubs naturally seek moisture. When concrete has cracks or porous joints, roots can enter, grow, and further displace or damage the structure, sometimes clogging flow or causing blockages.
Infiltration & Inflow (I&I)
I&I refers to unwanted water entering the system: infiltration via groundwater through cracks/joints etc., and inflow via direct connections (stormwater inlets, broken covers). Excess flow burdens treatment plants and drives up operational and regulatory cost. The EPA notes treating extra and unneeded flow costs municipalities millions. For example, one Tennessee study found I&I accounted for approximately 104,720 million gallons per year in that state, roughly 45% of annual influent to treatment plants (I/I Survey, George Kurz).
Structural Collapse & Leak-Paths
With enough cracking, corroded joint seals, or undermined base, concrete chambers can settle, shift, or collapse. Leaks lead to washouts, undermining of roadways, and public safety risks.
The ASCE 2025 Infrastructure Report Card assessed that the U.S. 's infrastructure as a whole earned a “C” grade (up from 2021’s C-), but its critical water categories like wastewater are still in the “D” range, which highlights the urgent need in fixing these systems.
Additionally, the EPA’s Infiltration/Inflow Program reports repeatedly acknowledge that excessive I&I isn’t just an environmental concern, it is a major fiscal burden on cities and their taxpayers as well. Issues like taxing treatment systems, violated permits and increasing maintenance costs are marking fiscal punishment on cities when a path out of it is readily available.
Polyethylene access chambers such as the Poo Pit address these failures and turn them into solutions:
- Corrosion Resistant & Watertight: Polyethylene doesn’t degrade under acidic or saline exposure like concrete does. Sealed, one-piece units dramatically reduce leaks and infiltration.
- Feature Freeze-Thaw Durability: Without porous cementitious material, polyethylene units are far less susceptible to freeze expansion and cracking.
- Root Resistance: Smooth, sealed walls without cracks or joints mean roots have no easy path to penetrate.
- Reducing I&I Cost: By blocking leaks and infiltration, treatment plants see less excess untreated water, lowering both regulatory risk and operational expenses.
- Structural Stable with a 100-Year Lifespan: Polyethylene chambers are engineered for long service (often ~100 years), minimal maintenance, and reduced need for repair or replacement, which ultimately limits risk of collapse, sinkholes, or trespass hazards.
Every smart city initiative begins with a strong foundation. Without durable access points underground, digital innovation above ground will always be at risk.
Municipalities ready to modernize their systems can start by replacing outdated concrete manholes with Poo Pit polyethylene access chambers. Take the first step toward smarter, safer, and more sustainable infrastructure.
