New member with black stain in vinyl liner still learning how to post to the forum

[garlatm]

Hi,

Water seemed perfect when leaving on short 4 day vacation.
Returned, opened pool and had black stains??? Will try to attach photo...

Water chemistry when we returned on 6/13/16 @ 2:07 PM:
FCL = 9.23
TCL = 9.59
Br = 18.0
PH = 7.3
ALY = 147
CH = 165
CYA = 79
Phosphates <100
Water temp was 90F due to recent heat wave

Tried PH reducer directly on stain; no noticeable effect?
Added "Algestroy" provided by Central Pool
Tried brushing today, 24 hours after adding algaecide... no joy!
Read this article and thought I try some of those recommendations: Know Your Stains| Pool Spa News | Water, Metal, Cleaning, Spas

Any thoughts?

Thanks!!!
Tom

 

[pooldv]

First thing I would try is the Overnight Chlorine Loss Test to see if there is some algae growing. If you have a trichlor puck you can try rubbing the puck on the stain for a few minutes. If the puck helps then the stain is organic and elevated chlorine levels and brushing will help. You will need an FAS/DPD chlorine test. You can buy it by itself at TFTestkits.net or in a TF-100 test kit.