Diamond Brite repair at end of last season, now black stain

[Mcaveman]

Last year the pool was new , I had a rust spot near a light in deep end, at end of season they drained pool cut out rust spot and patched, now seeing pool first time this season I have what looks like black sand stains on the deep end floor underneath where repair was made. Scrubbing does nothing

where should I start?

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[Texas Splash]

Before we assume the worse and that it's something related to the plaster work of before, try the following (deep end you might need to use a long pole to help):
- Hold a chlorine tablet at the area for a short time, move around a little as well (organic stain)
- Put some crushed vitamin c tabs in a nylon and hold against the area for a few (iron)
- Try some dry acid in a sock or nylon for a few (copper)

If those don't work, you do have the option of purchasing some Magic Jack's stain products, but you might also need to contact your builder if their work is still under warranty to ensure there's not a plaster issue. Let us know how things turn out. Good luck!

 

[Mcaveman]

I did try the vit c tablets in a sock, left it on for about 20 mins and after removing some of the black(very little) spread hit that eventually disappeared.