Help with rock hard calcium -- I think -- build-up issue

[reggie ho]

Hi all,

New to the forum and one year into pool ownership. I screwed up wtih extremely poor (non-existent) winterization and opened our pool up this spring to find crystals covering the walls of the pool. They have thankfully greatly diminished with keeping the ph low and scraping/brushing, but I still have rock hard build-up elsewhere that looks different than the crystals I was dealing with earlier. (I think it may have been there at least in part even last fall and I just didn't notice it.) It barely flinches when I scrub with pumice, and is more light gray in color than the white sharp crystals that I found this spring. I've taken some photos in case these help, and current pool chemistry below.

Based on a lot of forum and internet research, I think this might be calcium silicate (vs the calcium carbonate crystals that are mostly gone)? Anything you'd suggest based on the chemistry below to address these without draining and acid wash or resurfacing?

23,000 gal plaster resurfaced in 2015
FC 2.5
PH 7.3
TA 100 - 110 (varies from day to day so I'm probably somewhere in between.
CH 260
CYA 30 (per pool store)
Temp: usually kept at 85 degrees

Thank you!

 

[JoyfulNoise]

Silicates are rare. Sulfates are more likely. Are you using any sulfate containing chemicals like dry acid?

 

[reggie ho]

Thank you, and I used probably 10 pounds each of dry cyanuric and muriatic acid last fall but have been using liquid muriatic acid ever since and added just one five pound box of dry cyanuric acid this summer. Does this help? Thanks!

 

[mknauss]

There is no such thing as 'dry' muriatic acid. Dry acid is Sodium Bisulfate that Matt mentioned.

 

[JamesW]

Can you scrape some of the crystals up for a close up picture?

Try a drop of acid on the crystals.

 

[reggie ho]

Apologies, this is the product that I thought was dry muriatic acid but apparently is not: Amazon.com: Clorox Pool&Spa pH Down, 5-Pound 10005CLX (2 Pack): Sports & Outdoors

I tried scraping the scale that remains but it turns immediately to dust so small that I can't really capture it. The crystals that were along the wall that have since dissipated were tested with muriatic acid and did fizz, if that helps, but this looks like a different type of scale. It is much harder and is more gray in color than the white crystals I saw on opening the pool this spring.

Thanks, all. Also, I updated the calcium to 260 after reading after using my new Taylor test kit.