What is this?

[timopp]

Hi Everyone

New owner of old pool that we had replastered last year. When I took the cover off last weekend, the water was basically clear and I have been SLAMing this week. Here are current stats:

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Excalibur
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Build Type: Plaster
Volume: 28000 gallons
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Latest Test Result Summary:
FC: 13.2 (3 hours ago)
pH: 7.6 (yesterday)
TA: 80 (yesterday)
CH: 270 (yesterday)
CYA: 30 (yesterday)
==========================================

The water is very clear, but I have this brown looking stain going on. Very evident at winter waterline. I have been scrubbing, but they do not seem to be fading. My cholrine use is stabilizing so I will probably quit the SLAM today.

Any ideas or cures?

Thanks this is site and contributors are the BEST!!!

 

[Texas Splash]

Welcome! Try rubbing a Vitamin C tablet on the stains (iron).

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Your one-stop shop for all things TFP to include: ABCs of Water Chemistry, Recommended Chemicals/Levels, Test Kits, Troubleshooting, and much more!

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[timopp]

So I did try that and did not see much of a change. Mind you this over large areas of the pool. Perhaps unrelated, the robot is picking up a lot of silt and sand which I am assuming is from the plaster. Could this ne related?