Tankline was called in to remediate a drinking water tank serving a busy leisure centre. The tank had suffered significant osmosis, leading to blistering, delamination, and ultimately a failed Legionella test — making it a clear health and compliance concern.
This type of failure is common in older tanks constructed with polyester-based GRP panels, where the original gelcoat deteriorates over time. Polyester resins, although cost-effective, are prone to hydrolysis in constant immersion.
The gelcoat, intended as a protective finish, can microcrack, spider-crack, or develop pinholes due to thermal stress, UV exposure, ormechanical wear. Once compromised, water ingress leads to osmotic blistering — a process where water reacts with residuals in the resin, forming acidic byproducts that break down the laminate. This breakdown reduces hygiene and creates the perfect breeding ground for Legionella bacteria.
Our Solution
The answer was a full refurbishment using our Flex-Line system, a DWI-approved, solvent-free, flexible polyurethane coating specially designed for potable water environments.
Step-by-Step Process:
Surface Preparation
The internal surfaces were thoroughly sanded back to remove the degraded gelcoat and expose a sound substrate, ensuring long-term adhesion.
Coating Application
The Flex-Line system was applied in two contrasting coats — the first in cream, the second in blue — to ensure full visual coverage and compliance with QA standards.
Fast Return to Service
Thanks to its rapid cure profile, the tank was ready for refilling and use just 24 hours after the final coat.
The Result
A seamless, chemically resistant, and hygienic internal lining that restores the structural integrity of the tank and eliminates microbial risks —providing the leisure centre with peace of mind and long-term protection.
