Repairing Cracks in an Inground Fiberglass Pool

An inground fiberglass pool is one of the most popular choices for homeowners. The pool consists of a large molded structure, made of fiberglass and resins. It is coated with a gel to create a non-porous surface. The shell-like structure is then installed in the ground. In most cases, a concrete surrounding helps to secure the pool in place. Fiberglass pools are amongst the better known low maintenance pools. However, one of the biggest problems with these pools is the emergence of cracks.

Nature of Cracks

Spider cracks are hairline cracks that tend to develop in the gel coat of the fiberglass. Although this does not affect the structure, it spoils the appearance of your pool. Slightly larger cracks may reflect the normal wear and tear process. Very large cracks, that exceed 1/8 of an inch wide, or 1 foot in length, may indicate a foundational problem. It is best to have a professional come and inspect the pool in such cases, due to the complexity of the situation.

Repairing Spider Cracks

A patch kit obtained from a pool or marine supply store can help you repair hairline cracks. Be sure that the kit is suitable for a fiberglass pool. You’re unlikely to get satisfactory results if you use a repair kit meant for other items, such as a boat or roof, because of the chemicals in the pool. A patch kit comes with instructions on how to repair the cracks.

For larger cracks, follow the steps below.

1.   Drain the Pool

You must first siphon water from the pool with a hose or submersible water pump. Allow the pool to dry. Grind the crack with a die grinder, to create a groove in the fiberglass. Taper the edges of the groove, to facilitate a strong bond. Clean the surface with a rag and acetone to remove the dust and debris.

2.   Prepare Matting

Cut 5 to 7 layers of 4 ounce fiberglass matting. The first layer should be the smallest, as you’ll place it at the bottom of the groove. Cut each subsequent layer ½ inch larger. The final layer should be the largest, as you’ll place it on top so that it completely covers the crack and adjacent area.

3.   Prepare Resin and Apply

Mix fiberglass resin and catalyst in a small container. Apply some of the resin into the groove with a 4-inch felt roller. Place the smallest of the mats into the center of the groove and apply some resin. Roll the mat flat, and use a laminate roller to get rid of the air bubbles underneath the mat. Apply the next mat, and repeat the resin application followed by laminate roller. Repeat the process, until the groove is filled with the mats. Allow about 4 hours for the fiberglass to harden.

4.   Apply Gel Coat

Sand the area around the crack with a 400-grit sandpaper, followed by an 800-grit sandpaper. Use a clean rag and acetone to wipe away dirt and debris. Mix the gel and catalyst and apply with a paintbrush. Once the first coat has hardened, apply a second coat. Allow 24 hours for the gel coat to harden before you refill the pool.