Shadows on the bottom of my pool liner??


New member
Sep 2, 2010
Topic split off by Moderator

about 5 weeks ago i got what looked like staining under the liner of my pool. The liner is 11 years old and i have never had this problem before. Two things may have triggered it off !.
1. i bought a Floatron ioniser about 10 days before
2. i topped up the pool with a considerable amount of water from the mains

the guys looking after my pool took out the Floatron and after about a week the staining went.
yesterday morning the pool was clear and no sign of any staining but about an hour after i added wter from the mains i noticed the staining returning especially where the pool depth slopes away. PH is a bit high and chlorine is very low. Is this a question of balancing the chemicals or could it be more sinister. I live in france (not that that makes much difference)
Any help would be greatly appreciated.


New member
Sep 2, 2010
Melt In The Sun said:
Looks like it could be either an organic or metal stain, but we'll need more info to tell (of course :))

Can you post some test results (FC, CC, pH, TA, CH, CYA) and how you obtained them? How are you chlorinating? Do you have well water or an ionizer system?

I seriously doubt algae under the liner. Based on people's posts I've seen here, "algae or fungus under the liner" has always turned out to be stains on the surface, caused by either metals in the water or more commonly, insufficient chlorine.
Hi, i tried the vitmin c test and it looks like its a metallic stain. can you please advise as to how get rid of it if its possible thanks


TFP Expert
LifeTime Supporter
In The Industry
May 20, 2007
SWSuburban Chicago, IL
I think you're problem may be twofold.

Ditch the ionizer, stick to chlorine. Get your ph down to the recommended level and find yourself a good test kit. Maintain the chlorine level according to the CYA chart in my signature and you shouldn't have any issues.

I know this sounds like it "can't be that simple" but it really is. Once you get a good test kit (which may be difficult in France) post your full set of numbers for us so we can give you better advice, because right now this is my best guess.

Lastly, read Pool School. :)