Strange Yellow Stain

[jvsek17]

TFP Experts, need some help, please.

Situation:
Trying to sell my house and have a pesky yellow stain that is not coming out at deep end of pool (not helping).

Have brushed every day for last two weeks since pool water has been clear, no improvement.

Context:
Pool was closed for 2 years and had took almost 3 weeks to remove all organically and clarify water.

I have had a similar situation in the past on the shallow end of the pool because I have a heat pump and had metal residue I was able to remove with ascorbic acid.

I am not sure however if this stain is from 2 years of organics sitting at the bottom of the pool or a stain due to metal from the heat pump.

Current Chemistry:
- Water clarity is perfect
- Chlorine 10+ PPM (my pool guy added way too much shock about 2 weeks ago, still waiting for it to lower) but zero combined chlorine
- Alkalinity - 80
- PH - 7.2
- CYA - <40
- Phosphates - 1200

Advice Needed:
- Need help with a strategy. I understand this could be either a metal or organic stain, the latter less likely due to super high chlorine levels and very clear water.

- I understand I probably need to bring down my chlorine level, reduce phosphates and/or add chemicals (either metal remover or algicide). Just need help with order of operations here and what to try first.

- Metal stain? Algae?

- How can I optimize my pool chemistry to help remove the stain prior to adding more expensive chemicals?

Thanks in advance!!

 

[jvsek17]

 

[duraleigh]

Identify the stain first. Hold a trichlor puck in contact with the stain for about 3-5 minutes. If it lightens the stain is organic and chlorine and scrubbing will eventually remove it.

If that has no affect, crush up cheap vitamin C tablets in a sock and hold them down on the stain for 5 -10 minutes. If the stain is inorganic (calcium or iron), it will lighten it.

Report back the results.

Just guessing but it looks organic.

 

[jvsek17]

Thanks for advice, left chlorine tab on stain overnight, zero improvement.

Vitamin C sock lightened the stain in 30 mins. I think this is metal residue.

If I remember correctly, buy ascorbic acid and circulate in pool until stain comes out.

If an expert can confirm, that would be super. Also helpful to know what impact it will have on my chlorine and chemistry.

Thanks!

 

[duraleigh]

I am a little surprised. Is that stain about 1 x 2 feet or so? If so, I thinhk I would treat it with vitamin C tabs a little at a time. Seems like you could have it gone in 3-5 applications and save the trouble of an ascorbic acid treatment.

Is the liner stained anywhere else?

 

[jvsek17]

I am surprised too, to me it looked like an organic stain. Pool was closed for two years and had significant organics at the bottom, including sticks.

There are are two stains. One large crescent shaped about 3’x1’ and one smaller one 2’x0.5’. They lightened significantly with vitamin C so going for application #2 now, using pool brush to rub vitamin C socks then anchoring sock down in the darkest areas with the brush. Will let you know how it pans out.

My biggest worry is that there are 2-3 cigarette-burn looking stains in the area that are stubborn and it feels somewhat rough when I brush, but not sure because it’s 10 feet down. I’m worried there may be some damage to the liner. Liner is 3 years old and double-lined, no bubbles.

Fingers crossed. Thanks for the help and will report back.