algae? stuck to bottom, won't scrub off, SLAMing

[boogie0]

I recently bought a house with an in-ground cement pool with vinyl liner, 18x36. The previous owner had it professionally closed for the winter and we just opened it up. It was beautiful right before it was closed. It's a non-SWCG pool.


I have been SLAMing for about a week. The water was nasty but is clear now. However, the liner has what looks like some kind of algae on it. I cannot vacuum or scrub it off.

My FAS-DPD tests currently are:


ph 7.8
fc 37
cc 3
cya 70
calcium 180

Thanks in advance!

 

[jblizzle]

Welcome to TFP!

Have you felt the stains for roughness?
Could be metal staining. See if some crushed up vitamin c lightens the stain.

 

[boogie0]

Thank you!

I put some crushed up vitamin c tablets in a sock and ran it over the stains and they immediately disappeared. I repeated that exact method with no vitamin c tablets and it did not disappear.

I went to my local pool store for some ascorbic acid and they recommended that I wait a day or two for my FC to go down before adding it. Is that correct? Their FC test showed only 10ppm, but it’s still over 30ppm when I do it with my Taylor K-2006.

 

[mknauss]

Read this
Ascorbic Treatment to rid Pool of metal stains

Take care.

 

[pooldv]

Yes, that is iron stain, more here, Pool School - Metals in the Water and Metal Stains

 

[jblizzle]

How does the water look ignoring the stains? Is there any reason to suspect you may need to follow the slam process? I would at a minimum for form the overnight chlorine lost test to see if you should deal with anything in the water prior to dealing with the stains

 

[boogie0]

the water looks great if you ignore the liner

 

[imwarren]

You test result of CC - 3 indicates you still need to be SLAMing.
I think you want to complete you SLAM before dealing with the staining.

 

[boogie0]

FC finally dropped down so I added the ascorbic acid. It almost immediately cleared up the stains where it "landed" on the liner. However, there is still a large amount of stains where the acid did not fall, particularly in the center of the deep end. Do I simply need to add more ascorbic acid or will it eventually circulate around and clear up the center stains? It's been about 24 hours and has not improved beyond it's initial results. My filter is set to circulate and not filter, as per the directions.

Thanks so much for all the help so far!!