Dark brown stains

[jcoira]

Hi experts,

I am new to the site, but have been reading for a couple of weeks now trying to find answers to my stain problem. I keep my PH and chlorine under acceptable levels at all times, yet around two or three weeks ago I noticed a couple of dark spots (dark-brown when you look closely) that have quickly spread all around the bottom of my in-ground pool. I tried Jack's Magic Stain Identification kid with no luck. None of the packages seemed to make a difference when applied to the stains, as directed. I have uploaded pictures that I hope help ID the stains. The stains appear to be black in the pictures, but if you zoom in you will see they are actually dark brown (dark red?)

Please help.

 

[Butterfly]

Welcome to TFP!

Have you tried the vitamin C test to determine if the stain is metal? Place a cheap vitamin C tablet on the stain for a minute or two. If you can't easily reach the stain, crush some vit c tabs in a sock and hold it on the stain with a pole for a minute or two. If the stain lightens after being exposed to vitamin C, it is a metal stain.

If you rub the stain with a trichlor tab or hold the tab on the stain for a minute or two, and the stain lightens, then it is an organic stain.

It would be helpful if you posted a full set of test results and let us know how you maintain your chemicals.

 

[JamesW]

Is this a fiberglass or concrete pool?

Can you feel the spots?

 

[jcoira]

What I have at home is a basic kit that allows me to test chlorine and PH only. I usually do my own readings every other day and take a water sample to my local pool store every other week for a most complete test. Current readings are:

Total chlorine 3.0 ppm
Free chlorine 3.0 ppm
PH: 7.4
Total Alkalinity: 100ppm
Calcium hardness 325ppm
Stabilizer: 60ppm

I tried both the vitamin C and trichlor tab tests before posting to the forum for the first time, but the stains don't react to it.

I can't feel the stains.

It is a concrete pool.

 

[duraleigh]

Rather than a stain resulting from pool water chemistry, that looks like something that has fallen into your pool.

Have you tried to scrape them off?

 

[jcoira]

I haven't tried that. I was hoping I could remove them without damaging the surface.

How would you do it?

 

[jcoira]

>>that looks like something that has fallen into your pool.

All I can think of:

1- I noticed one of my sprinklers is getting treated water into the pool. I mix the sprinkler water with something called had water 2000 and with grass so green.
2- Particles of fertilizer could be falling into the water when grass is fertilized. Not sure what type of fertilizer they use.
3- I bought and started using one of those solar pool chlorinators a couple of weeks before the stains appeared for the first time.

I should add that I applied some muriatic acid on one of the stains and it didn't work either.