Plumbing in the Home/Shower Pan Caulk


Hi Dana,
I have a fiberglass shower that was pro installed a few years ago. After a few years the caulk started to come up between the pan and the vertical walls. I cleaned off the old caulk carefully. I tried using a few weak chemicals (supposed to be safe for fiberglass) to help remove but was careful not to use strong ones. It took a lot of manual labor to clean up the old caulk using razor blades etc. After a few months it peeled again. I again carefully cleaned and repaired with 100% silicone. It is coming up again. Each time it starts to separate at the bottom corners along the horizontal surface. Any ideas?

Hi Fred,
Most annoying! I'm not aware of anything in the way of caulking that works better than silicone. Once set, there really isn't any kind of solvent you can use to remove it one cured. Silicone caulk manufacturers often recommend mineral spirits for cleanup of uncured material.

I think that may be the problem here. The surface needs to be very clean and dry for the best adhesion. This may just be one of those ongoing maintenance chores one needs to do every few months. Obviously newly applied caulk must be allowed to cure well, possibly for a day or more before use. It will "skin over" and appear to be cured when the center of the bead in the deeper areas is still fluid.

That being said, this actually is not such a critical area. There is a substantial overlap of the walls over a flange of the shower pan, 1 to 1 1/2 inches at least. This will pretty much prevent any water from getting behind the shower walls by itself unless you managed you've flooded the fan above the rim and that's pretty hard to do since the water would likely just run out the front.
Good Luck,

Plumbing in the Home

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Dana Bostick


Pretty much any residential plumbing questions. For "item specific" details such as a specific model of fixture, I will need to research and there may not be any useful information available. Note: I live and work in Southern California. We do not, as a rule, use hot water or steam heating systems, oil fired boilers or private water wells so my knowledge in those areas is pretty limited. There are others here on AllExerts that can probably answer those questions better.


Retired, Licensed General Contractor with Plumbing license. Active Home Inspector, Litigation Consultant and Infrared Thermographer, Online Marketing specialist.

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