Mildew on sand under liner

Newdude

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Jun 16, 2019
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NY
I would bleach it. 10:1 usually works but I always go 50/50. I have seen similar mold/mildew show through thinner liners. It won’t hurt anything under the new impervious liner but it’s possible you will see it.
 

duraleigh

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Apr 1, 2007
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Bleach......hands down. 50/50 or thereabouts......per haps a little weaker.

Interesting how it got there. It seems to me that mold/algae needs somew water and maybe so air. Was the pool empty for a while?

Nevertheless, sand smoothed back out and it should not happen again.