A small crack in a water tank rarely stays small for long.
Whether the tank is constructed from GRP (glass-reinforced plastic) or steel, structural stress, ageing and environmental factors can lead to fractures. While hairline cracks may initially appear cosmetic, they often signal deeper issues that can compromise water hygiene, structural stability and regulatory compliance.
Understanding what causes tank cracks, and when intervention becomes urgent, can prevent costly failure and unplanned downtime.
Why Do Water Tanks Crack?
Water tanks operate under constant internal pressure while being exposed to external temperature shifts and structural movement. Over time, this combination creates stress.
In GRP sectional tanks, cracks commonly develop due to panel fatigue or joint movement. As the material ages, it can lose flexibility, making it more susceptible to stress fractures.
In steel tanks, corrosion is often the root cause. Once protective coatings fail, oxidation weakens the substrate. As corrosion progresses, metal thickness reduces, eventually leading to perforation or cracking.
Thermal expansion is another major factor. Tanks expand in warmer temperatures and contract in colder conditions. Repeated expansion cycles weaken seams and joints, particularly where coatings have already begun to deteriorate.
How Cracks Escalate Over Time
A crack alters how pressure is distributed across a tank. Instead of uniform load bearing, stress concentrates around the damaged area. With every fill cycle, that pressure widens the fracture incrementally.
Moisture ingress accelerates the problem. In steel tanks, water reaching exposed metal speeds up corrosion. In GRP tanks, seepage behind panels can affect insulation and compromise structural integrity.
Left untreated, what begins as a minor fracture can lead to joint separation or significant leakage.
The Hygiene and Compliance Risk
Structural cracking is not just a mechanical issue, it becomes a water hygiene issue.
Cracks create uneven internal surfaces that allow sediment accumulation. Rough or deteriorated internal linings also provide harbourage points for bacteria, increasing contamination risk.
This is particularly concerning in potable water systems, where tank condition directly affects water quality standards.
Professional relining systems help address this.
Covac specialises in GRP and steel tank repair and relining using WRAS-approved and DWI-listed polyurethane coatings, including Acothane DW. These coatings restore a smooth, seamless internal barrier and are backed by a minimum 10-year guarantee.
When Does a Crack Require Immediate Action?
Not every surface blemish requires full replacement, but certain signs indicate urgency.
If you notice damp patches around the tank base, visible internal splitting, bulging panels or unexplained drops in water levels, the crack may already be compromising structural integrity.
A professional inspection will determine whether the tank remains structurally sound for repair and relining, or whether replacement is necessary.
Repair vs Replacement: What’s the Smarter Option?
Full tank replacement can be disruptive and expensive, especially in commercial or industrial environments where downtime impacts operations.
In many cases, structural reinforcement combined with internal relining provides a more efficient solution.
Once repair is made, a high-performance polyurethane lining then seals the internal surface, preventing further deterioration and extending lifespan.
Relining can significantly extend tank service life without the need for full replacement.
Why Early Intervention Matters
Cracks rarely self-stabilise. They either remain static for a short period or progressively worsen.
Addressing structural issues early offers several advantages:
- It prevents secondary corrosion or fibre damage
- It maintains hygiene standards
- It avoids emergency leak response
- It reduces overall lifecycle cost
Proactive repair is almost always more cost-effective than reactive replacement.
Ignoring the issue risks escalation. Acting early protects both infrastructure and water quality.
Contact COVAC for a professional tank assessment. Our team will inspect the extent of cracking, identify the root cause and recommend a compliant, long-term solution.
