What problem am I looking at?

[Jimrahbe]

Hi,

I have become the pool boy for my two unmarried daughters who both have pools. I’ve attached pics of one of the pools and would like to know if the problem is the fact the pool is about 10 years old or if it is something that can be fixed. The issue is worse around the pool drain, but is also present in a lesser degree at other places in the bottom of the pool. The problem does not appear to be on the sides of the pool at all. Not sure if the step edges have the same issue or if they are just worn down. If anyone recognizes the problem, please let me know what I need to do to fix it.

PH = 7.4
FC = 4.5 (End of day reading)
CC = 0.0
TA = 70
CH = 450
CYA = 80
Using BBB only since we bought the house about a year ago.
Water is clear as a bell.
Using TF-100 test kit and cheap electronic PH tester

Thanks,
Jim R.

 

[JasonLion]

Welcome to TFP!

Are those areas rough, or smooth? In the picture it looks like a combination of etching and staining, but if smooth it is just staining.

I would try placing a vitamin C tablet on one of the stained areas and see if anything happens. That will narrow down the possibilities a fair bit.

 

[Jimrahbe]

Thanks Jason,

For the most part, the colored areas are just as smooth at the clear white areas, except around the main drain where the colored areas are just slightly rougher than the white areas.

I put three Vitamin C tablets on the bottom of the pool held in place by new pieces of tile. Near the main drain there was no noticeable change. At another place in the pool where the colored areas are there, but not as bad, there was a small black spot where the tablet had dissolved. I also put a tablet in a white area of the plaster and WOW.. When it dissolved, it left a large black spot about 2 “ in diameter.

Although I did what you said, I have no idea what I was doing or what the results show. What to give me a clue?

Thanks again,

Jim R.