New member
Apr 17, 2019
Plano, TX
This is a 15 years old pool, I have owned it since last year. I use the method I learned from this website to maintain my pool.
The most recent test data is like this
- Location:Texas
-Chlorine : 10 (only add liquid chlorine from local Pinch A Penny store, twice a week and about 0.8-1 gal each time recently)
-PH:7.6 (need constantly add acid to lower PH value)
- Stabilizer: 60
- TA: 100
- Calcium:220 (this is slight low and i didn't do anything about it

Everything is fine, no algae, nothing I noticed abnormal until recently I notice some discolored spot in the pool bottom, only a small area as shown in picture. it feels like some kind of corrosion, the surface is not as smooth as other area
The reason I think maybe
- the discolored place is mostly located at where I usually pour liquid chlorine, sometime I poured liquid chlorine in early morning before the pump starting time therefore that area may have high chlorine for a while sometime.
- Is it because the calcium is low in my pool? The calcium is a little low and I didn't do anything about it

Any suggestion? Can I do anything or replaster is the only solution?


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Mod Squad
Gold Supporter
LifeTime Supporter
Jan 17, 2012
Evans, Georgia
Hi there....welcome to TFP posting. :)

Have you ever poured Muriatic Acid in that spot? It can lay heavy on the bottom if water from a return isn't carrying it away and diluting it. And I personally always brush when using that.

I'm not sure if liquid chlorine would cause that but powdered can.

Have you added any of those things?

Maddie :flower:


Mod Squad
TFP Expert
Bronze Supporter
May 3, 2014
Laughlin, NV
Pool Size
Salt Water Generator
SWG Type
Pentair Intellichlor IC-40
always dilute it in a big bucket of water first
It is not necessary and added risk to dilute muriatic acid in a bucket.
Simply pour it slowly at the return jet with the pump running. If you like, brush the area to disperse.
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