Mop Sink Waterproofing and Leak Prevention Using Belzona 3121

KHIA ID: 10150
Industry: Commercial Facilities (COMM)
Application: FPA-Floor Problem Areas (FPA)
Substrate: Concrete
Customer Location: 8550 Casa Verde Road Orlando, FL 32827 United States
Application Date: December 2025
Products: Belzona 3121 (MR7)
Problem: Water was leaking through the gap between the mop sink and the surrounding wall and floor areas. This allowed water to bypass the sink and infiltrate the building structure, causing water damage and leaks on the floors below. The existing sealant had failed, and repeated exposure to water and cleaning chemicals increased the risk of ongoing leakage, deterioration of surrounding substrates, and maintenance issues throughout the facility.
Mop sink with visible gaps around drain and wall joints causing water leakage.

Mop sink showing water infiltration points around the drain and wall interfaces prior to repair. Gaps between the sink, walls, and drain allowed water to escape the basin and leak to lower floors.

Drain penetration waterproofed with Belzona 3121 MR7 system.

Close-up of the drain penetration sealed using Belzona 3121 (MR7) to prevent water migration around the pipe connection.

Waterproofed mop sink using Belzona MR7 system.

Completed repair using Belzona 3121 (MR7), creating a continuous waterproof seal directing water into the drain and preventing further leakage.

Application Situation
Water was leaking through the gap between the mop sink and the surrounding wall, allowing moisture to migrate behind the sink and into the building structure. This resulted in water infiltration to lower floors, creating maintenance issues and the risk of damage to adjacent areas.

The Belzona solution provided a fast, in-situ repair without removing the sink, breaking walls, or disrupting operations. This significantly reduced repair time, labor costs, and avoided repeated water damage while delivering a long-term waterproofing solution.
Application Method
The area around the mop sink was thoroughly cleaned and dried to remove dirt, residue, and contaminants. The joint between the sink and the wall, as well as the drain outlet area, was prepared to ensure proper adhesion.

Belzona 3121 (MR7) was applied directly to the gap between the mop sink and the wall to create a continuous waterproof seal. Belzona 9331 reinforcing sheet was embedded into the first layer where required, followed by a second coat of Belzona 3121 to fully encapsulate the joint. The drain outlet was also reinforced to prevent future leakage. The system was allowed to cure, forming a seamless, flexible, and watertight barrier.
Belzona Facts
Belzona 3121 (MR7) is a cold-applied, moisture-tolerant waterproofing system that can cure even in damp conditions. It eliminates the need for demolition, hot work, or extended downtime.

This solution provides long-term protection against water ingress, reduces maintenance costs, and allows facilities to remain operational during repairs, making it ideal for commercial and public facilities with repeated leak issues.
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