How to Fix a Crack in a Fiberglass Hot Tub

Drain the water from the tub and allow it to dry overnight. Spread a towel over its drain to keep it from clogging with debris during the repair procedure.

Don a dust mask and safety glasses to prevent inhaling or getting the fiberglass shard in your eyes. Scruff the crack and the area around it vigorously with sandpaper.

Rub a rag dipped in acetone to remove debris around the crack in the tub or wipe the surface with a moist cloth.

Mix the fiberglass repair filler with the hardener according to label directions. Insert the prepared filler inside the crack using a putty knife. Allow the filler to harden for the time specified on the label instructions.

Sand the surface of the hardened filler and surrounding surface with a 200-grit palm sander. Scuff the edges of the repair filler until it blends with the surrounding area.

Wipe the repair surface with a rag dipped in acetone. Frame the repaired section of the tub and 3 inches around it with lengths of duct tape.

Cut three strips of 9-ounce fiberglass cloths provided with the repair kit. Keep the first quarter-inch smaller than the length of the crack and the other two progressively smaller.

Soak the smallest strip in the gel mixture and lay it over the crack. Run a felt roller over the strip to remove trapped air bubbles and help it adhere to the crack. Repeat the process of soaking and laying the other two strips over the repair area. Leave the strips to dry overnight.

Match the shade of the last layer of gel mixture with a colorant. Read tinting directions on the colorant label. Apply a thin layer of gel coat over the patched surface and leave it to dry overnight.

Remove the lengths of duct tape and sand the dried fiberglass strips with 80-grit sandpaper until the surface of the patched section blends into the tub. Rub the surface with a clean cloth.