Liner staining or algae? Getting obsessed..

Rob_LI

Member
Jul 11, 2019
17
Suffolk Long Island (NY)
hi all -- i've been using this site for a long time but i can't seem to figure out if my pool is on the verge of an algae attack or if the liner is just stained. sorry for the long post, but i wanted to give as much info as possible.

there's some very light greenish patches on the pool floor that i can only see when it's cloudy and if i have sunglasses on. i also notice the color in the creases by the wall where the deep end starts. my water is clear and i've been pretty good over the years maintaining it. my main concern now is CYA. after doing some searches and reading posts, i finally understand that years of using pucks may have put me in a tough spot (i've gotten buckets of tabs from a family member so it was zero cost).

when i opened the pool, i SLAM'd it, adding several gallons of 12.5 liquid chlorine. pool was clear, no problem. however i kept noticing these lightly colored patches. mind you, the liner is pretty bleached this year and the floor is white in some spots (this is where i see the green color). i'm wondering now if the color is the mix of chlorine and the blue liner making green?

anyway, one day i went to the pool store to get the water tested (terrible, i know.. but up until a week ago i was still using test strips out of laziness..). CYA reading was 149 and FC/TC in the upper 20's. funny, pool store said CYA level was fine..lol.

i bought a CYA test kit of amazon, the Blue Devil one. did a reading and CYA was 100. drained some water, replaced it, came down to 70. then i decided to get the Taylor kit mentioned on TFP. CYA on this one shows 100 (just checked it too, like 5 minutes ago).

here's my current numbers:
FC 15
TC 15
CYA 100
pH 7.6
TA ~150

i've maintained FC inline with the CYA chart for weeks by adding the 10% liquid chlorine from Walmart. is it possible i have a dormant algae issue or is it likely staining? when in the pool i tried to rub with a rag and nothing came off. i also noticed a stain here or there from possible acorns or something from the winter.. same thing, didn't come off.

thanks in advance!
 
Welcome to the forum!
Can you get a sock of crushed up vitamin C on the stain? That will tell you if it iron, or if it darkens it, copper. If no effect, take one of those pucks and set it on it for a few minutes. Does it remove the stain? If so, then it is organic.

I suggest you read ABC's of Pool Water Chemistry and consider reviewing the entire Pool School eBook.
 
Also the test kit can't measure over 100. You should mix half pool water with half tap water and re-do the CYA test to see if you can get a reading using that.
 
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