What Is Manhole Rehabilitation? Benefits of Manhole Coatings and Linings

What Is Manhole Rehabilitation?

Manhole rehabilitation is the process of restoring aging manholes and reinforcing the structure to avoid needing to fully replace the manhole. While replacement may be the only option for manholes that are damaged beyond repair, sewer manhole rehabilitation is ideal for situations in which the manhole can be restored through trenchless methods. 

Common Causes of Manhole Deterioration

Understanding the causes of manhole deterioration is important when selecting the most effective manhole rehabilitation strategy. Many aging manholes show visible signs of damage, but the underlying issues often stem from a combination of environmental, structural and chemical factors. Identifying these root causes can help guide manhole repair, lining and coating solutions. 

Hydrogen Sulfide Corrosion

One of the most common causes of manhole deterioration is hydrogen sulfide (H₂S) corrosion, which occurs when H₂S gas from wastewater reacts with moisture and bacteria to form sulfuric acid. This acid attacks concrete and mortar surfaces, leading to severe internal degradation.  

Groundwater Infiltration

Groundwater infiltration is another major issue. When external water seeps through cracks, joints or failed seals, it not only damages the manhole but also overwhelms wastewater systems with unwanted flow. Over time, this leads to inflow and infiltration (I&I) problems that stress the entire sewer network.  

Structural Stress

Structural stress from traffic loads and freeze-thaw cycles can contribute to cracking and joint displacement in manholes. While these conditions may require additional structural repairs, coatings and linings play a critical role in sealing cracks, preventing water infiltration and protecting the newly repaired surfaces. 

Poor Initial Construction

Poor initial construction, use of substandard materials or lack of proper joint sealing can leave manholes vulnerable from the start. Without durable protective coatings or linings in place, these structures are more susceptible to early failure and deterioration. 

The Benefits of Sewer Manhole Rehabilitation

Commercial properties, industrial facilities and municipalities can benefit from manhole rehabilitation. Trenchless manhole rehabilitation products and methods can revitalize existing infrastructure, prevent disasters and restore the integrity of the system for years to come. 

Extends Lifespan 

Manhole lining systems protect the substrate from daily wear and tear as well as chemical attacks, corrosion and other damage, extending the lifespan of the manhole regardless of shape, condition or material. 

Solves and Prevents Inflow and Infiltration Issues

Damaged manholes are vulnerable to inflow and infiltration issues caused by excess water from storms or the ground seeping through holes or cracks in the manhole system. If left unaddressed, these issues lower the capacity of the sewer system, increase operational costs and damage the infrastructure. Protective linings, in conjunction with chemical grouts, solve existing inflow and infiltration issues as well as prevent the development of future challenges. 

Prevents Corrosion

Corrosion caused by hydrogen sulfide (H2S), microbes, or environmental conditions damages the structure of concrete manholes or the mortar joints of brick manholes. Over time, this corrosion leads to serious deterioration of the manhole infrastructure. Installing an anti-corrosive manhole rehabilitation product prevents or slows the development of corrosion in the structure. 

Increases Cost Savings

Replacing a manhole is expensive—not only the initial digging but also the rebuilding that follows. Alternatively, a manhole rehabilitation project provides significant cost savings because there is no digging, building or downtime required. 

Reduces Downtime

Manhole replacement requires facilities and municipalities to halt operations while crews and their equipment work. The manhole rehabilitation process, on the other hand, does not require any digging and does not disrupt daily operations. In most cases, sewer manhole rehabilitation crews can finish the job in 12 hours or less. 

The Process of Manhole Rehabilitation: 3 Common Applications

There are many technologies that can assist with sewer manhole rehabilitation without the need for additional excavation. Products like cured-in-place (CIPM) manhole liners, cementitious lining systems and polymer coating and lining systems help stop leakage, prevent corrosion, enhance the structure and extend the service life of the manhole. 

1. Cured-in-Place Manhole (CIPM) Liners

CIPM liners are tubes made of a variety of resins and other materials that are inserted into the manhole and inflated until it is tightly secured to the interior. As the tube is inflated, the resin hardens and provides strong, long-term chemical resistance. 

The use of a CIPM liner requires that the manhole is large enough for the inflated tube to fit into. If the manhole chimney is not wide enough, it may need to be removed so the CIPM liner can be placed into the widest part of the pipe. Additionally, the bottom of the manhole must be designed with a seal that will ensure nothing gets between the liner and the substrate while it is being inflated. 

Installing CIPM liners often requires more equipment and larger crews than other manhole rehabilitation methods. However, they can be an effective and affordable option for rehabilitating traditional, cylindrical manholes. 

2. Cementitious Manhole Lining Systems

Cementitious mortar lining systems are specially formulated to provide a permanent seal on the interior of the manhole corridor. They are applied with a low-pressure spray or a trowel and can be installed quickly, with less downtime. 

These liners act as a protective shield and are often reinforced with fibers to provide extra crack resistance and tensile strength. Unfortunately, their chemical resistance is not as strong as polymer-based lining systems, so they are not ideal for corrosive environments. 

3. Polymer Manhole Coating and Lining Systems

Polymer coating and lining systems include products made from epoxies or polyurethanes. These systems are applied by hand with a trowel or via a pressure sprayer and are designed to protect the structure of the manhole from corrosion, chemical attacks, wear and tear and impacts. 

When polymer liners are installed correctly, they provide protection and support the structure for years. If the manhole is already corroded, use cementitious mortar liners to build the manhole back to its original shape. Then, after the polyurethane or epoxy liner is applied to the interior of the manhole corridor, it fully seals to the substrate. The result is an impermeable, durable, chemically resistant, anti-corrosive, environmentally safe shield that cures quickly and provides long-term protection. 

Epoxy or polyurethane liners are the ideal sewer manhole rehabilitation solution. 

Choosing the Right Manhole Coating and Lining System

Selecting the right manhole lining system is critical to the long-term success of any manhole rehabilitation project. Several factors should influence your decision, including the extent of existing damage, exposure to corrosive elements and the desired service life of the structure. 

Ultimately, using polyurethane or epoxy coatings and linings for manhole rehab ensures the highest level of protection, especially in high-risk, high-demand wastewater environments. 

Polymer Manhole Lining and Coating Solutions from Sherwin-Williams

Anti-Corrosive, Chemical-Resistant Manhole Coatings and Linings

Sherwin-Williams manhole lining and coating solutions offer superior chemical resistance—even in harsh sewer and wastewater environments where manhole infrastructure is exposed to high levels of hydrogen sulfide, ammonium, sodium, sulfuric acid, sulfates and other aggressive chemicals. Our products fully adhere to the substrate and create an impermeable barrier that prevents it from being exposed to chemicals, moisture and other agents that would damage the surface. 

Additionally, Sherwin-Williams manhole coating and lining systems are anti-corrosive. Whether the substrate is exposed to environmental hazards, atmospheric damage or corrosive elements, our coating and lining solutions prevent corrosion and support the long-term service life of the manhole. 

Durable, Long-Lasting Manhole Coatings and Linings

Sherwin-Williams epoxy and polyurethane manhole lining and coating solutions are extremely durable and can withstand the daily wear and tear, impacts and abrasions of sewage and wastewater environments. The quick and easy application and curing process reduces the risk of significant downtime and ensures operations can continue as planned. Regardless of the manhole material, the coatings and linings tightly adhere to the substrate and application—or, when needed, reapplication—is a painless process. 

Our manhole linings and coatings serve as a functional barrier and are specifically formulated to provide impermeable, waterproof protection for the long term. When properly installed, our manhole coating and lining products last for years with minimum maintenance, touch-up, or cleaning requirements. Thanks to their superior durability and chemical resistance, they are built to be long-lasting. By applying a Sherwin-Williams manhole coating system, you can enhance performance, reduce maintenance costs over time and extend the life of manhole infrastructure. 

Shop Manhole Rehabilitation Protective Coatings and Linings at Sherwin-Williams

Sherwin-Williams is the leading provider of coatings and linings for the water and wastewater industry. Our line of high performance sewer and wastewater collection coatings and transmission pipe linings offers superior resistance to corrosion, impacts, abrasions and chemical attacks. With our durable, flexible and long-lasting lining and coating solutions, you can extend the service life of your sewer and wastewater infrastructure and experience cost savings for years to come. 

Contact a Sherwin-Williams Coatings Specialist today  to learn more about our epoxy strong, low-maintenance, anti-corrosive and chemical-resistant coating and lining products for sewer systems and manhole rehabilitation projects. 

Manhole Rehabilitation FAQ

What is a manhole lining?

A manhole lining is a protective internal layer applied to the interior surfaces of a manhole structure. It creates a barrier that prevents corrosion, chemical damage and water infiltration, helping to extend the life of the infrastructure. 

What is a manhole coating?

A manhole coating is a surface treatment applied to protect the exterior or interior of a manhole. It serves to shield the structure from environmental exposure, chemical attack and physical wear caused by sewage, water or gases. 

When is full manhole replacement necessary?

Although manhole rehab can extend the life of most structures, there are times when full replacement is the only option. Severe structural failure, advanced corrosion or complete loss of integrity may make manhole restoration unfeasible. An inspection by experienced professionals can help determine whether manhole coating or lining systems will suffice or if replacement is required. 

How long does manhole rehabilitation last?

Depending on the system used, manhole rehabilitation can extend service life by 25–50 years or more.