Help Identifying Stain

[justincinmd]

I’ve noticed some white spots have started to show up in my pool, particularly on the sun shelf and in the edges. I’m hoping someone can help me identify it. I think it’s probably calcium scale, but I am seeing rocks in the pool vacuum. I’m hoping they’re just residual from an acid wash that had to be done last year for scaling, but any to make sure.

The CSI is generally between 0 and 0.3, though it’s definitely been more positive in the past. I added a CO2 system which has the ph much more under control.

 

[Texas Splash]

Welcome to TFP! You think it may be scale, however you also mentioned having an acid wash last season. Are these white areas new since that acid wash? If you typically maintain a positive CSI, then it's certainly possible. Also, can you post a full set of water test results either with your TF-100 or Taylor K-2006C test kit?

 

[justincinmd]

Using the Taylor kit, I get:

FC: 3.0
TA: 100
CYA: 80
TEMP: 86
pH: 7.4
CH: 525
CSI: 0.08

The white areas are new since the acid wash. The pool was new in February of last year, and there were finish problems initially. The company that did the finish said it was badly scaled because the pool company didn't properly care for it in the first 30 days, so they drained it and acid washed it. White stains are just now starting to creep back in.

I just got rid of my pool company and am now maintaining it myself now. There were really serious problems keeping the pH down in the first year because the pool company was keeping TA relatively high (120) and the big waterfall causes significant aeration, so we weren't able to use it much. They could drop the pH to 7.2 and it would be back up above 7.8 the next day.

I put in the CO2 system so I could run the waterfall consistently without the pH pushing over 8. It is usually around 7.6 in the mornings now after the waterfalls run all night without the filter pump/co2 system on. After those have been on a couple of hours, it drops to 7.4 and stays there.

I'm hoping that the white spots in the above attachments are just calcium scale from the pH going high before I took things over, and the rocks are left over loose pebbles from the acid wash that just weren't vacuumed up, and there's not etching or something else like that going on.

 

[Texas Splash]

You can try maintaining a slightly negative CSI range (-0.3 to -0.6) for a few weeks/months to see if that helps loosen that fresh scale. To help lower the TA, let the pH rise to about 7.8-8.0 before knocking the pH down to 7.0 Each time you do that it should help. At TA of about 60 should work nicely.