A crack in your swimming pool is more than an eyesore — it’s often the reason your water level keeps dropping. In Cape Town, shifting clay soils, ground settlement and ageing marbelite make pool cracks especially common. The key is knowing which cracks are cosmetic and which are costing you thousands in lost water and hidden damage.
Why do swimming pools crack?
- Ground movement. Cape Town’s clay-rich soils expand and contract with the seasons, flexing rigid pool shells until they crack.
- Settlement. Poor sub-base preparation or soil settling under the pool causes structural cracks.
- Age and porosity. Old marbelite and concrete break down, craze and crack over time.
- Hydrostatic pressure. Groundwater pushing up against an empty or poorly drained pool.
- Tree roots and nearby construction.
Types of pool cracks
- Surface (crazing) cracks — fine, spider-web cracks in the finish only. Usually cosmetic, but they let water into porous marbelite and worsen over time.
- Structural cracks — wider cracks through the shell itself. These leak and need proper repair before they spread.
How to tell if a crack is serious
Signs a crack is leaking or structural:
- The water level drops faster than evaporation (more than ~1–2 cm a week)
- The crack is wide, long, or growing
- Damp patches or movement in the surrounding paving
- Visible cracks around lights, steps or fittings
If you suspect a leak, our pool leak detection guide helps you confirm it.
How pool cracks are repaired
- Inspection & leak confirmation to find every crack and hollow spot.
- Crack stitching / routing — structural cracks are routed out and stitched or reinforced so they can’t reopen.
- Filling & hollow-spot repair — drummy, delaminated areas are cut out and rebuilt.
- Resurfacing or relining — because a patched crack in porous marbelite often returns, the lasting fix is a new surface over the whole pool.
When a reline is the real fix
A single hairline crack can be spot-repaired. But if your pool has multiple cracks, ongoing leaks, or a porous, failing surface, patching is a short-term fix. A fibreglass reline seals the entire pool in one seamless, crack-resistant shell — the permanent solution. See the signs your pool needs resurfacing.
Can you repair a pool crack yourself?
Tiny cosmetic cracks can be patched with pool putty, but DIY rarely holds on a leaking structural crack — and getting it wrong wastes water and money. Proper routing, stitching and resurfacing is specialist work.
What does pool crack repair cost?
Minor spot repairs are relatively inexpensive; a full reline (the permanent fix for a cracked pool) runs roughly R600–R850+ per m² for fibreglass. A free on-site assessment gives you an accurate figure.
Frequently asked questions
Are pool cracks serious?
Surface crazing is usually cosmetic, but structural cracks leak and worsen over time. Any crack that lets water out should be repaired promptly.
Why does my pool keep cracking?
Most often it’s ground movement in Cape Town’s clay soils flexing a rigid shell. A flexible fibreglass lining handles that movement far better.
Can a cracked pool be fixed without rebuilding?
Yes — crack stitching plus a fibreglass reline seals and reinforces the pool without a full rebuild.
Stop the leak at its source
👉 Next steps: Get a free quote · Our pool services · Fibreglass pool lining in Cape Town · Contact Aquatic Pools
Related articles: Signs your pool needs resurfacing · Why your pool is losing water · Fibreglass vs Marbelite
