[Grey Spain appears while adding soda ash]

On 3/19/2021 at 10:02 PM, Robr said:

What type of pool surface?  CH level (or full pool test results).  If plaster, how old?

I'd guess when you added the soda ash to one area,  it created a VERY high local pH.  This caused the staining.

This either caused calcium to deposit on the surface (possibly w trapped dirt) or caused a metal to stain.  

Rub a vitamin c tablet or several of them broken up in a sock, and rub on the stain - a metal stain should lift but scale (calcium) won't.  If it's metals, keep the pH 7.5 or lower.  Scrub with more Vitamim c / ascorbic acid.  If it's a larger area you may need a whole pool metal treatment.  Test your water for metals, remove/fix the source, and be careful to avoid high pH and high FC levels.  

Both types of stains may lighten or lift over time with pH held on the lower side (below 7.5, faster at 7).  If your pool is plaster, apply muriatic acid from a squeeze bottle or pole applicator, plus scrubbing nay remove it.

There are other possibilities, esp with plaster, but this seems most likely to me.

 

 

 

[Grey Spain appears while adding soda ash]

I am looking for advise on an issue that occurred to me yesterday.

My pools PH and alkaline has been low.  I have been adding 2 pounds of soda ash a week plus alkaline plus for several weeks and yesterday my Ph was 6.8 and alkaline was 40 and chlorine was a 1.  I felt I was almost there so I added 1/2 pound of soda ash and 1/2 pound of alkaline plus.  I always dilute in a bucket of water before adding to pool. However, when I added chemicals to pool almost immediately a grey stain appeared near where I added chemicals. I have tried to brush but will not remove.  Any suggestions on how to remove this stain.