Sealing ducts below the water table

The project:

• Sealing below-ground cable duct penetrations in a concrete structure where the ducting sat below the water table and groundwater ingress was present during installation

The client:

• Major utility provider

The products:

• Running water kit and Filoseal+ (FILOform running water kit)

The challenge:

Sealing ducts below the water table creates a specific installation challenge. (And one that will almost certainly lead to an incorrect job without the right knowledge and solutions in place.)

Where cable ducts enter a below-ground chamber or concrete structure, groundwater can (will) enter the duct.  This then create continuous pressure at the point of entry.

In this project, the penetrations were exposed to active water ingress because the ducts were positioned below the water table. That meant the contractor was not just dealing with damp conditions, but with running water that could interfere with the installation of the permanent duct sealing system.

Without controlling that flow first, water could continue to enter the structure and could also compromise the quality of the final seal.

So, a method was needed that would manage live water during installation. All, that is, while delivering a long-term sealing solution for the cable entries.

The solution:

FILOform supplied the running water kit as part of the sealing method for these below-water-table duct entries.

The kit was used to deal with running water in the duct while the permanent seal was being installed. A temporary water block was created inside the duct using non-hardening plastic waterproofing sealant (damming putty) and tap components, allowing the installer to control the water flow during the sealing process.

This approach helped prevent running water from compromising the permanent sealing system during installation. Once that troublesome water flow had been controlled, Filoseal+ was fitted in front of the water block on a clean, dry section of duct. (In line with the installation method for the system.)

Then, after the curing period, the tap was turned off. This allowed the contractor to complete the duct sealing works in difficult wet conditions, without water pressure compromising the finished seal.

This project demonstrates the importance of building around actual site conditions. Here, the installation methodology was specifically engineered to accommodate and mitigate water ingress from day one.

Les principaux avantages du projet étaient les suivants :

• Controlled sealing in ducts affected by running water
• A practical method for sealing below-water-table duct entries
• Reduced risk of water compromising the permanent seal during installation
• Filoseal+ installed on a clean, dry section of duct
• Running water controlled before final closure
• Long-term protection against groundwater ingress into the chamber

Installation overview:

• Water ingress: Water can enter the duct due to its position below the water table
• Damming back water: To prevent water from interfering with the seal during curing, you apply putty to the surface of the hex sleeve and insert a drain
• Purpose of the drain: The drain is left open to relieve water pressure, preventing it from pushing the seal out while it cures
• After curing: Once the curing period is complete, the drain is closed/turned off

This method ensures the seal remains intact and effective, even in wet or submerged conditions.

The results:

By using the running water kit together with Filoseal+, the contractor was able to complete the duct sealing works in active wet conditions while maintaining the integrity of the permanent seal.

The installation method allowed the team to manage live water at the duct entry, create the right conditions for the permanent seal, and then turn off the tap once curing had been completed. This provided a practical and controlled approach to sealing cable ducts below the water table.

For projects like this, successful water ingress prevention depends on multiple factors. While this absolutely includes the sealing material, it also includes expertise and installation know-how.

In this case, the running water kit helped the contractor deal with the reality of running water in the duct, while still achieving a durable long-term sealing outcome.

Key outcomes:

• Helped prevent groundwater ingress into the chamber
• Controlled running water during installation
• Reduced the risk of seal failure caused by water pressure at the point of entry
• Improved the installation conditions for the permanent seal
• Supported long-term protection of below-ground cable duct penetrations