Fibreglass

How it is built

The shell is moulded in a factory. River Pools, a US fibreglass pool manufacturer, describes the layers: an outer gelcoat surface, then a resin layer, then chopped fibreglass laminate set in resin. It names polyester and vinyl ester as the two resin options. The same manufacturer notes that water molecules can pass through the gelcoat, but algae cannot embed in the surface the way it can in porous concrete.

On site, the shell is lowered into a prepared excavation, levelled, connected to the pipework and backfilled. Because it arrives as one piece, its size is limited by what can be transported and lifted into place, which matters for villas with narrow access.

Typical problems with age

• Osmotic blisters. River Pools explains that water can pass through the semipermeable gelcoat, mix with polyester resin and collect beneath the gelcoat, forming bubbles. The manufacturer describes these blisters as cosmetic and says they do not damage the structure of the shell.
• Fading, chalking or staining of the gelcoat.
• Fine cracks in the gelcoat, often around steps and fittings.
• Leaks at fittings where pipes, lights and skimmers pass through the shell.
• Walls pushing in or the floor lifting if ground water acts on a lowered or empty shell.

What repairs usually involve

Gelcoat repairs, blister treatment and resealing of fittings are specialist work. Small areas can often be repaired locally. Widespread cosmetic problems may lead to refinishing the whole surface.

Some repairs need the pool to be lowered or emptied, and this is where fibreglass needs particular care. River Pools warns that problems can happen when the ground water around a pool is higher than the water inside it, that side walls may push inward and the floor may lift, and that only authorised fibreglass pool professionals should drain a pool. It recommends checking and removing ground water before draining, and notes that most manufacturers require an authorised dealer to drain the pool or the warranty may be voided.

River Pools also says a pool should only be drained when a necessary repair requires it. Green water or ordinary debris are not reasons to drain.

Leaks at fittings are usually traced in the same way as in other pools, with a leak detection specialist testing each fitting and pipe in turn while the water stays at its normal level.

UAE notes

Ground water conditions vary from site to site, so ask a specialist to assess them before any work that lowers the water level. If your pool is still under warranty, check with the manufacturer or installer before any repair, and ask what the gelcoat warranty says about colour change in strong sun.

What to tell a specialist about your pool

• Manufacturer and model of the shell, if known, and who installed it.
• Age of the pool and any warranty documents.
• What you see: blisters, cracks, stains, fading or water loss.
• Whether the pool has ever been drained, and what happened.
• Access to the garden for equipment.
• Photos taken in daylight, close up and wide.