A plastic shower pan can withstand years of use without cracking or damaging if the installation is done properly, but accidents can still happen. Small cracks and pits in a shower pan aren’t a reason to panic, since you can restore the pan to almost new with a little bit of patching. Bearing in mind that preparation and practice are the key to making superficial repair invisible, there are several ways that you can bring your pan back into working order via epoxy, caulking and patch kits.
Cleaning the Pan
Before you make any repairs, first clean the shower pan so that any repair compounds used actually adhere to the pan. As a general rule a good scrub with a household bathroom cleaner and a scrub brush is enough to remove the soap scum and other buildup from the pan. From there, rinse the pan out and let it dry for at least 24 hours before making any repairs. If there is still water present, soak it up with a rag to ensure the pan is dry.
Hairline fractures that are barely visible with the naked eye, but are caught during regular washing of the shower pan, are not a reason for panic. As a general rule these are simply stress fractures as a result of weight over time on the pan. An application of a silicone-based caulk quickly and easily patches the crack and ensures that no water is leaking through it. For best results, use a transparent silicone to allow the color of your shower pan to remain visible. Smooth the caulking down with your fingers to force it into the crack and coat the pan area surrounding it.
Gelcoat and other patch kits are available at home improvement centers specifically for use with shower pans. As a general rule they come with the filler and the hardener, and come in a variety of colors. They can also be dyed to more closely match a shower pan’s color, but bear in mind that matching the exact color of the pan is an impossibility. Instead, be content with “as close as you can get.” Smaller cracks (up to 1/8 inch) can be filled with the gelcoat and hardener. Larger cracks (up to 1/4 inch) must also use a fiberglass mesh that is placed over the crack or hole and adhered with the mixture. After it dries, the patch must be sanded to match the surrounding shower pan. Always follow manufacturer instructions, as they vary by brand.
Epoxy is another solution to filling in cracks and voids in a shower pan up to 1/4 inch in width or 1/2 inch in diameter, as a general rule. The principles are the same as with gelcoat, except that epoxy hardens far more rapidly and is harder than a gelcoat. Application timing is key when using epoxy, as you must fill the void and then sand it down before it has a chance to completely harden. Each brand has specific instructions and generally comes in two parts that are mixed together. Similar to gelcoats, you can go for a quick fix and just use the base color of epoxy, or add dyes and pigments to the epoxy to try and match the color of your shower pan.
Anything larger than 1/2 inch in width or diameter may be a sign of underlying issues with the home. In addition, cracks that work their way across the entire shower pan as opposed to just a small area may be indicative of a problem with the structural integrity of the home. For any crack or hole larger than 1/2 inch, consult a structural engineer to determine the underlying cause.