Swimming Pool Yellow Stains

[Porfyrios Vasileiou]

I have a swimming pool at home 1.5 years old and has some yellow stains on the floor near the edges of the pool.

I tried adding chloring first and run for a few hours, then algecide and run for a few hours.

I tried brushing but it doesnt do anything.

The chlorine levels are now a bit higher than normal due to the added chlorine and the ph level is quite up.

What can i do to identify what this is and how do i fight it guys?

Thanks in advance!

I have attached some photos of the stains.

[waterbear]

First, how high is your chlorine? You cannot test pH when sanitizer levels are high because of a chemical reaction between the pH indicator dye and the high chlorine level. 

https://www.poolspaforum.com/forum/index.php?/topic/58991-false-high-ph-readings-when-shocking-some-truths/

First thing is to detetmine if the staining is organic ot from metals in the water. Yellow stains are usually from iron 

Get a vitamin C tablet and place it on one of the stained areas. If it is iron the stain will disappear within a minute where the vitamin C is in contact with the stain.  

Report back after you do this.

 

[waterbear]

5 hours ago, skyhenge said:

Yellow stains near the edges of the pool are usually caused by either mustard algae or metal staining. Since brushing and chlorine didn’t work, metal staining is more likely.

Mustard algae brushes away easily but it is hard to kill. Organic stains from leaves and such can stain yellow to brown.

 

5 hours ago, skyhenge said:

To test, press a vitamin C tablet on a stain for about 30 seconds. If it fades, it’s metal-based (likely iron). If it doesn’t, try a chlorine tablet and if that works, it’s mustard algae.

Close but no cigar. You are correct about vitamin C and iron stains but the chloirne tab is a test for organic stains, not mustard algae.

To treat iron stains you would use Ascorbic acid.

[saunaguy]

Those yellowish stains around the edges definitely look like they could be mustard algae super stubborn and doesn’t always respond to regular chlorine or algaecide. First thing I'd try is scrubbing the spots with a chlorine tablet directly (wear gloves), see if it lightens up if it does, then it’s probably organic. Also double check your filtration and circulation, mustard algae loves still water. If it doesn’t lighten at all, it might be metal staining  like iron in which case you’d want to try a stain remover specifically for metals and possibly use a sequestrant. Keep the pH in check too high pH can make both algae and metal stains more of a pain.