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Old 10-29-2018, 11:24 PM   #1
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Default Caulk for showerpan

I recaulked the shower pan with ProFlexRV caulk. https://www.amazon.com/Geocel-28101V.../dp/B004RCP49O

I fully removed the old caulk and cleaned with mineral spirits before applying new caulk.

About 1 year has gone by since I did this.

It does not seem to adhere well to the fiberglass walls however as it has developed several cracks along the caulk and the wall. I suspect there is a lot of flex when driving, causing the caulk to release in places along the wall leaving a visible "gap".

What type of caulk have others used here? Just basic bath/shower silicone type caulk, or something that is more specific to RV use, and in turn the flex that will occur.

Thanks for suggestions.
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Old 10-30-2018, 12:53 AM   #2
Mike DZ
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Default Re: Caulk for showerpan

Hmm, I used Geocel as well, without the problems you note. However, if you think the problem is too much flex, there is a caulk called "Big Stretch" - name says it all. Please note that Big Stretch does not stand up to abrasion or chemicals well.
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Old 10-30-2018, 04:12 PM   #3
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Default Re: Caulk for showerpan

It took me awhile to find a caulk that would stick to both the shower walls and the pan...

At last I settled on Dow Corning RTV-739 Plastic Silicone Adhesive White - 10.1 oz Tube.


I used short pieces of hydraulic hose to form contoured beads.
I abraded the contact surfaces with very fine wet/dry sand paper.
I cleaned all contact surfaces with IPA before, during and after sanding.
Test dabs of 739 on both the shower wall and pan yielded good adhesion.

This product requires 7 days per .25" depth at 50% humidity to cure properly...

It's held up well for three years now and shows no sign of losing it's grip.

Note: There have been several posts over the years stating that some shower pans did not lay flat against the floor. The result was when an occupant put their weight on the shower pan close to the perimeter the pan would flex up and down which resulted in the caulk/sealant pulling loose from the wall. The solution was to remove the shower pan, apply new adhesive to the floor, replace the shower pan and weight it down evenly across all surface areas until the adhesive cured. So - if/when old caulk is removed test for up/down flex around the perimeter of the shower to determine if the shower pan needs to be R&R'd... Beware that R&R shower pan is a MAJOR project! Ask me how I know:-)

Last edited by onemanvan; 10-30-2018 at 08:55 PM.
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Old 10-30-2018, 04:46 PM   #4
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Default Re: Caulk for showerpan

Another option: Sika Sanisil Sanitary Sealant (anti-mold/microbiol)

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Old 11-15-2018, 12:24 AM   #5
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Default Re: Caulk for showerpan

3m 4200
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Old 11-15-2018, 01:13 AM   #6
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Default Re: Caulk for showerpan

I have no experience with the particular RV shower. I do have some experience with repairs involving sealants.

You first need to use a tested proven product. Most higher end name brand products fit the bill, but if cost is a priority there are less expensive sealant/adhesives that do fine. Research will be needed to identify those products.

Proper cleaning and surface prep is required or even the most expensive products will not perform properly.

If movement and flex are an issue, mesh can be added to the sealant. The mesh adds strength. The top layers of sealant can be tooled or otherwise smoothed so that the mesh isn't visible.

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