Mottling on the pool floor

SAMTUCKER

New member
Mar 11, 2024
2
WASHINGTON STATE
March 28, 2024
Good Afternoon,
I have a 5 year old gunite pool. I am a new pool owner, so I trust there is a lot to learn. I perform water tests every third day. (PH, chlorine, alkalinity, hardness, CYA, etc. And then take the appropriate action. I keep the PH between 7.2 and 7.4. The alkalinity seems to be very consistent at 75. The hardness does vary between 350 and 400. The water temperature is 88 to 89 degrees. (Yup, I like it warm. I am in Washington state).
My issue is a brownish/grayish/yellowish modeling that is appearing on the bottom of the pool. The Hasa Chlorine I use does not remove it. I work towards keeping the chlorine level around 2.40. ( I was using chlorine tablets, but the CYA was extremely high. So I changed to the liquid HasaChlor).
Scrubbing it with my nylon pool brush does not remove it. Scrubbing it with a nylon scotch-brite type pad does not remove it.
Muriatic acid does not remove it. It is not slimmy, so I'm thinking it is not an algae, of some sort. The end of the pool with more of this modeling
does feel slightly more 'textured', than the end that does not have so much modeling. The pool manufacturer, came out with a diamond pad and tried that. It did not seem to have any effect either. It appears to me like a 'creeping stain" of some sort. I've been reading your form. I tried the Vitamin C, test. It did nothing
to the modeling. As a pool-rookie, what have I done wrong? What needs to be done to get my white pool, back to white?
 
Welcome to TFP.

What test kit are you using that gives you TA of 75 and FC of 2.4?

Post pics of your pool and the stains.

Post a full set of water chemistry in the format:

FC
CC
pH
TA
CH
CYA
 
Welcome to TFP.

What test kit are you using that gives you TA of 75 and FC of 2.4?

Post pics of your pool and the stains.

Post a full set of water chemistry in the format:

F
CC
pH
TA
CH
CYA
I use the Taylor Test Kit.
FC: 2.40
CC: -0-
PH 7.30
TA 75
CH 375
CYA 30

Attached is a photo of the pool floor. One must enlarge the picture in order to see the mottling. (I do not have an underwater camera).

Thank you in advance for your help/advise.
Sam


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How do you get a TA of 75 when each drop is 10 ppm?

Your FC is too low for your CYA a level.
FC/CYA Levels
How do you chlorinate your pool?

What chemicals have been used in the pool?

If the stains are creeping then it is likely metal stains. Have you taken your water to a pool store and had then test it for metals?
 
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