CSI with waterline tiles

ka8yiu

Gold Supporter
Aug 11, 2016
180
SW FL
Having a fiberglass pool, I have always followed advice I got here that a negative CSI, down as low as -.6, was OK. But, I actually have waterline tiles, and was wondering if I should be maintaining a higher CSI to avoid the grout from being damaged. Thoughts?

Kevin
 

mknauss

Mod Squad
TFP Expert
Bronze Supporter
May 3, 2014
43,967
Laughlin, NV
If the grout is cement based, yes.

It is far better to use silicone grout for tile on a fiberglass pool.
 

ka8yiu

Gold Supporter
Aug 11, 2016
180
SW FL
The tiles were in place when I bought the house. I’m pretty sure they’re cement based. Do you think a silicone grout and spreading a layer over the grout lines could help to waterproof and protect them so leaching is not a problem?
 

mknauss

Mod Squad
TFP Expert
Bronze Supporter
May 3, 2014
43,967
Laughlin, NV
I would not do that. The grout hopefully was epoxy based when applied. Do you get cracking or water wicking up the grout lines leaving calcium scale or algae, above the water line?
 

ka8yiu

Gold Supporter
Aug 11, 2016
180
SW FL
I would not do that. The grout hopefully was epoxy based when applied. Do you get cracking or water wicking up the grout lines leaving calcium scale or algae, above the water line?
I do not get any scaling, but occasionally one of the small lower tiles comes free and I have to reattach and re-grout it.

I can’t say I’ve noticed any water wicking, but occasionally I get a little tinge of green right along the waterline in a very small spot. Quick little brushing takes care of it.
 
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