The good news: most common fiberglass pool problems, including gelcoat spider cracks, bulging or buckling walls, color fading, osmotic blistering, shell flotation, surface stains, and even plumbing issues caused by ground settlement, usually trace back to one of two causes: poor installation or poor water maintenance. If you're planning to build a fiberglass pool or already own one, especially in the UAE, knowing these risks early helps you avoid costly repairs and protect a long-term investment. Here's what actually goes wrong, why it happens, how proper installation, material quality, and routine care prevent it, and what to ask your pool contractor before the pool goes in.
1. Spider Cracks in the Gel Coat
What it looks like: Thin, web-like gelcoat spider cracks in the gelcoat surface appear as small, hairline cracks that often show up as short 1–3 inch lines; they are usually cosmetic and do not affect structural integrity unless they are deeper fractures, though they can still be unsightly and let moisture reach the layers beneath.
What causes it: Spider cracks are almost always the result of flexing in the shell where it isn't properly supported, typically from incomplete or improperly compacted backfill around the pool during installation, though localized stress on the gel coat, manufacturing stress, or minor impact can also trigger them. When the ground beneath or beside the shell isn't packed correctly, the shell has room to flex under water pressure and ground movement, and the gel coat, which has far less flexibility than the fiberglass laminate beneath it, cracks under that repeated stress.
How to avoid it: This comes down almost entirely to installation quality, and proper installation reduces the risk of spider cracks forming. A properly backfilled pool, using the correct material (typically sand or gravel per the shell manufacturer's specification) and compacted correctly in stages as the shell is filled with water, gives the shell full, even support with no room to flex. This is a detail worth asking any contractor about directly before construction begins. Minor cosmetic cracks can be monitored, but deeper structural fractures should be assessed for professional repair.
2. Bulging or Buckling Walls
What it looks like: Visible waviness or an inward/outward bulge in the pool wall, sometimes subtle, sometimes obvious enough to see from across the yard, especially along the fiberglass pool walls.
What causes it: Wall bulging is usually caused by improper backfill material or other improper backfilling conditions. Saturated sand backfill or the wrong backfill material can create uneven pressure and hydrostatic pressure against the pool shell, leading to inward or outward wall movement. Without full, even support behind the shell, water pressure from inside the pool or ground pressure from outside can slowly deform the pool walls over time.
How to avoid it: Proper backfill, ideally gravel backfill where the manufacturer allows it, should be compacted properly in stages while the pool is filled with water so pressure stays balanced on both sides during pool installation. Good installation practices matter because installation quality has a major effect on long-term performance, and a quality job can help a fiberglass pool last up to 40 years. If bulging does happen, repairs usually mean excavation and repacking with the right material
3. Color Fading and Discoloration
What it looks like: A gel coat that's lost its original vibrancy, gone patchy, chalky, or shifted toward yellow, green, or a washed-out version of its original color.
What causes it: Two things, usually together: prolonged UV exposure causing colour fading as the gelcoat breaks down over years of sun exposure, and poor water chemistry, especially extended chemical contact from low alkalinity or high chlorine, that accelerates oxidation of the surface. Dubai's climate makes this a more relevant concern than it would be in a milder climate, given how many hours of intense direct sun a pool surface receives across a year.
How to avoid it: Consistent water balancing is the most controllable factor here: routine testing should keep pH between 7.2 and 7.4 and total alkalinity between 80 and 120 ppm, all within the recommended ranges, to prevent the chemical side of fading almost entirely. On the UV side, choosing a quality gel coat with UV-resistant pigment technology at the outset helps, and in modern fiberglass pools darker gelcoat colors show fading more readily than lighter colors, so a lighter finish is often the safer choice if matching appearance over time is a priority. With proper care, good chemistry can significantly extend gelcoat life; standard gelcoat can last 25 to 30 years, and while fading is mostly aesthetic, it can make a pool look older than it is.
4. Osmotic Blistering
What it looks like: Small, raised bubbles on the gel coat surface, usually a few millimetres across, sometimes appearing in clusters. If pierced, they may contain a small amount of liquid.
What causes it: This is the one fiberglass pool problem that traces back to manufacturing quality rather than installation or maintenance. Osmotic blistering occurs when water penetrates the gel coat. Water can then seep through blistering areas, react with soluble materials in the laminate, and create trapped moisture pockets between the gel coat and resin that push the surface outward. It's more common in older pools and in shells manufactured with lower-grade resin systems.
How to avoid it: This is almost entirely a manufacturer selection issue and is primarily a manufacturing quality issue, so choosing a reputable manufacturer and a quality manufacturer matters. Shells built with a proper vinyl ester resin barrier layer behind the gel coat are specifically engineered to resist water penetration, and modern pools using that system are incredibly durable and have dramatically lower rates of osmotic blistering than shells built with lower-grade polyester resin. This is a genuinely important question to ask any pool contractor: what resin system does your shell manufacturer use, and does it include a dedicated moisture barrier layer. If problems do appear, repairs can be handled properly by a professional to avoid mismatched colors or the wrong resin application, and they often cost about $1,000 to $5,000.
5. Shell Flotation (Popping Out of the Ground)
What it looks like: In the most serious cases, an empty or partially drained fiberglass shell can actually lift or shift out of its excavation entirely, a dramatic and expensive failure.
What causes it: Fiberglass shells are lightweight relative to their size, which is part of what makes them fast to install, but it also means an empty shell can be pushed upward by groundwater pressure beneath it if it's drained (even partially) in an area with a high water table. This is a genuinely important consideration in Dubai and other coastal UAE areas, where groundwater levels can sit relatively close to the surface, particularly near the coast.
How to avoid it: Never fully drain a fiberglass pool without a clear plan and, ideally, direct guidance from your installer, and never do it in a high water table situation without hydrostatic relief measures in place (such as a properly installed hydrostatic valve at the base of the shell, designed specifically to release groundwater pressure during draining). This is precisely the kind of detail a proper site assessment and soil/groundwater evaluation should catch before your pool is ever built, and it's a strong argument for having a genuinely experienced local installer rather than a generalist contractor unfamiliar with UAE ground conditions.
6. Surface Staining
What it looks like: Discoloration in patches or streaks, often brown, green, or rust-toned, distinct from overall fading since it tends to appear in specific areas rather than uniformly across the surface.
What causes it: Mineral buildup (particularly relevant given the UAE's generally hard water), metal content in fill water reacting with pool chemicals, or organic debris and chemical residue accumulating over time without regular cleaning.
How to avoid it: Regular water testing and balancing prevents the chemical side of staining, while routine brushing and cleaning prevents organic buildup from ever settling into the gel coat surface. If your fill water is notably hard, a sequestering agent added during fills can help prevent mineral staining before it starts, worth asking your maintenance provider about directly.
7. Plumbing Issues From Ground Settlement
What it looks like: Unexplained water loss, or damp patches in the decking or surrounding landscaping.
What causes it: This isn't unique to fiberglass pools, but it's worth knowing about regardless. Pool plumbing runs beneath the deck and pool structure, and if the ground beneath it wasn't properly compacted during installation, or if improper backfilling shifts support and stresses connections around the shell and plumbing runs, gradual settlement over months or years can misalign or crack the pipes running underground, leading to slow plumbing leaks that are genuinely difficult to spot from the surface.
How to avoid it: This again comes back to installation quality, specifically proper soil compaction and correctly bedded plumbing runs at the time of construction. If you notice unexplained water loss beyond normal evaporation (which itself is significant in Dubai's heat), it's worth having plumbing checked before assuming it's simply evaporation.
8. Limited Shape and Size Options
What it looks like: Not a defect, but a genuine tradeoff worth naming honestly: fiberglass shells come in manufacturer-set moulds, so you're choosing from a design catalogue rather than a fully custom shape.
Why this happens: It's inherent to how fiberglass pools are made, pre-moulded off-site and delivered as a single shell, which is exactly what makes them faster and less expensive to install than concrete. The tradeoff is fixed shapes and a practical size ceiling (roughly 8-10 metres for most residential installations).
How to work with it, not around it: For most homeowners with standard villa pools, rectangular, Roman-end, or beach-entry designs under 8-10 metres, this simply isn't a real limitation, since modern manufacturer catalogues now offer a wider range of shapes, sizes, and built-in features than many expect; Thursday Pools, for example, offers multiple model types. If your design ambitions go beyond that (a fully custom free-form shape, an infinity edge, or a pool longer than 10 metres), that's a legitimate signal to consider concrete construction instead, and an honest contractor should tell you that directly rather than trying to force a fiberglass solution onto a design it isn't suited for.
The Common Thread: Installation Quality Is What Actually Matters
Look back through this list, and a pattern emerges: most fiberglass pool issues and other pool problems trace back to installation, ongoing maintenance, or manufacturing quality rather than the material itself. That includes many of the most common fiberglass pool problems, and choosing a reputable manufacturer plus an experienced installer makes a big difference in long-term performance. Issues like spider cracks, bulging walls, shell flotation, plumbing settlement, and to a real extent color fading are tied largely to installation quality; osmotic blistering points more to manufacturer resin quality, while staining and shape limitations are maintenance and design tradeoffs rather than defects.
This is the honest takeaway: a well-manufactured shell, properly installed by a contractor who understands UAE ground conditions and follows correct backfilling, compaction, and plumbing procedures, avoids nearly all problems with fiberglass pools entirely. The risk in fiberglass pools isn't really the material, it's cutting corners during installation.
What to Ask Any Fiberglass Pool Contractor Before You Sign
What resin system does your shell manufacturer use, and what quality control and manufacturing process standards does a reputable manufacturer follow to reduce blistering risk?
How do you handle backfilling and water-filling sequencing during installation?
What backfill material do you use, is it compacted properly, and how do you prevent uneven support around the shell?
Who will install the pool, and is that crew experienced with fiberglass pool installation specifically to avoid installation issues?
Have you assessed groundwater levels and soil conditions for my specific site?
What warranty do you offer on the shell structure versus the gel coat finish?
If gelcoat damage occurs, what repair process do you use, and how do you avoid color mismatch?
Can I see examples of pools you've installed that are now several years old, not just recent projects?
A contractor confident in their installation process should be able to answer all of these clearly and specifically, not with vague reassurance. For a deeper look, pay attention to whether the answers stay detailed and consistent rather than general.
What resin system does your shell manufacturer use, and what quality control and manufacturing process standards does a reputable manufacturer follow to reduce blistering risk?
How do you handle backfilling and water-filling sequencing during installation?
What backfill material do you use, is it compacted properly, and how do you prevent uneven support around the shell?
Who will install the pool, and is that crew experienced with fiberglass pool installation specifically to avoid installation issues?
Have you assessed groundwater levels and soil conditions for my specific site?
What warranty do you offer on the shell structure versus the gel coat finish?
If gelcoat damage occurs, what repair process do you use, and how do you avoid color mismatch?
Can I see examples of pools you've installed that are now several years old, not just recent projects?
