Fiberglass pools are praised for their smooth surface, low maintenance, and long-lasting construction. At the heart of that glossy, clean finish is the gelcoat—a protective outer layer that seals the fiberglass shell and gives it its signature look and feel. But when problems arise with the gelcoat, they can impact both appearance and functionality.
This guide covers the most common fiberglass pool gelcoat problems, why they happen, and how to fix or prevent them, whether you’re dealing with discoloration, chalking, or cracks.
1. Gelcoat Discoloration or Staining
Quick Answer: Gelcoat discoloration in fiberglass pools is typically caused by mineral deposits, chemical imbalances, or metal staining from water sources.
What It Looks Like:
- Yellow or brown staining (iron)
- Green or teal tinge (copper)
- Dark or cloudy spots (organic buildup or scaling)
How to Fix:
- Use a metal sequestrant like Natural Chemistry Metal Free to bind metals and prevent oxidation.
- Apply ascorbic acid directly to stained areas for effective spot treatment.
- Brush and balance water chemistry after treatment to prevent recurrence.
Tip: Avoid using harsh acids or scrubbing pads, which may scratch the gelcoat and void your warranty.
2. Gelcoat Fading or Chalking
Quick Answer: Fading or chalky gelcoat occurs when UV rays and oxidization degrade the resin, leading to a dull or dusty finish on the pool’s surface.
Signs You’ll Notice:
- Loss of shine or glossy appearance
- White or gray chalky residue on hands after touching the surface
- Discoloration in high-sun exposure areas
Fix It:
- Polish and restore: Use a fiberglass-safe polishing compound such as Meguiar’s M4965 Marine Restoration Kit for gentle oxidation removal.
- Apply a protective wax: Marine-grade waxes can help restore shine and block UV damage.
Prevent It: Maintain proper water chemistry, especially pH and chlorine, and use a pool cover during long periods of direct sunlight.
3. Gelcoat Cracks or Crazing
Quick Answer: Hairline cracks or “crazing” in the gelcoat can develop from thermal expansion, impact stress, or improper installation. These are usually cosmetic but can worsen over time.
Causes of Cracking:
- Sudden temperature shifts (cold water refills on hot surfaces)
- Ground movement or pool settling
- Sharp impacts or misuse during cleaning
What to Do:
- For minor surface cracks: Wet-sand the area with 600–1000 grit sandpaper and apply a gelcoat repair paste.
- For larger or deep cracks: Hire a professional to inspect for structural damage beneath the gelcoat.
Recommended Product: Try Evercoat Marine Gelcoat Repair Kit for color-matched, DIY-friendly surface fixes.
4. Gelcoat Blisters or Bubbles
Quick Answer: Blisters in the gelcoat form when water seeps into microscopic gaps and reacts with unsealed resin, causing pressure and bubbles under the surface.
Signs of Blistering:
- Small raised bubbles or soft spots on the pool walls or floor
- Visible discoloration or pinholes where blisters burst
Repair Process:
- Drain the pool (if needed) and sand the blistered areas
- Clean and dry the surface thoroughly
- Apply a fiberglass-compatible gelcoat filler or repair compound
Pro Tip: If widespread blistering is present, full resurfacing may be needed. Contact a fiberglass pool restoration expert for large-scale repairs.
5. Gelcoat Delamination
Quick Answer: Delamination happens when the gelcoat separates from the fiberglass layer beneath it, often due to poor bonding, moisture penetration, or aging.
What You’ll See:
- Bubbling or lifting of the gelcoat layer
- Soft or hollow-sounding spots when tapped
How to Handle It:
- Cut away the delaminated area and sand down to solid fiberglass
- Fill the area with a gelcoat resin repair compound
- Sand, polish, and re-seal the surface after it cures
Best Practice: Regular inspections and sealing prevent moisture intrusion that leads to delamination.
6. Rough or Pitted Surface
Quick Answer: A rough gelcoat surface is usually the result of calcium scale buildup or prolonged chemical imbalance, especially in pools with high pH or calcium hardness.
What to Do:
- Brush the surface: Use a soft-bristle brush to remove loose scale.
- Balance water chemistry: Keep calcium hardness at 200–400 ppm and pH between 7.4–7.6.
- Use a scale remover: Apply a product like ScaleTec Plus to dissolve hardened buildup.
Preventative Tip: Use a weekly sequestrant or chelating agent to prevent mineral bonding to the gelcoat surface.
Fiberglass Pool Gelcoat Maintenance Schedule
| Frequency | Task |
|---|---|
| Weekly | Test pH, chlorine, calcium, and alkalinity |
| Monthly | Brush pool walls with soft brush, apply sequestrant |
| Quarterly | Inspect surface for cracks, chalking, or discoloration |
| Annually | Polish and apply UV-protectant gelcoat wax if needed |
When to Resurface or Replace Gelcoat
If your fiberglass pool shows extensive fading, cracking, or blistering across large areas, simple touch-ups may not be enough. Resurfacing is the best long-term fix.
Signs It’s Time to Resurface:
- Persistent surface chalking or color loss
- Widespread gelcoat cracks or pits
- Delamination or structural exposure
Pro Recommendation: Hire a certified fiberglass resurfacing contractor to reapply a new gelcoat layer or a hybrid epoxy coating for extended life.
Conclusion: Keep Your Gelcoat Smooth, Bright, and Problem-Free
Fiberglass pools are low maintenance, but gelcoat problems can arise without proper care. From discoloration and chalking to cracks and blisters, most issues are preventable with regular maintenance and the right treatments.
Need to restore shine or fix surface damage? Use the recommended kits and products above, and maintain balanced water chemistry to keep your gelcoat smooth, strong, and stunning for years to come.