Getting ready to SLAM, but sides of pool look a little off...

[Exlonghorn]

I was setting up to SLAM to correct a mild algae problem, but measured a very high CYA level. Partially drained the pool to correct the CYA level, and that uncovered numerous light patches on the top edge of the pool walls. Care to venture a guess at what this is about?

 

[mknauss]

Can you post test results? There are none shown in the Poolmath log you are sharing.

Most likely scale.

 

[Exlonghorn]

Took me a bit to figure out how to log via the app. Took these measurements after I replaced 4,100 gal of an estimated 20K gal pool. Got the CYA down to 90...still high but more manageable. We're expecting rain so that should add another 1K gallons.
FC = 12.5 (I'd added liquid bleach during the draining because I couldn't circulate)
CC= 0
TA=140
pH=7.7 (and then added 42oz of muriatic acid to correct the pH and TA)
CYA = 90
CH = 180
The pool surface is roughened where the white patches are present (looks like it removed/etched the pool surface rather than added something on top of it). My goal, for now, is to get the water balanced and maintained going forward.

 

[mknauss]

If etched, the pH was sub 7 for a long time. Long term use of pucks?

 

[Exlonghorn]

I've been diligent about maintaining the pH and have always had it between 7.2-7.7, but I've only had this home for 18 months and it was built in 2010 (and I'm assuming the pool was put in when the house was built). I made the ignorant mistake of relying on Trichlor pucks and Calcium Hypochlorite shock as a sanitizer for the past year, which eventually put the CYA over 140 (but still kept the pH where it should be). I've now shown up here, received some better education, shut off the tab feeder, and stocked up on liquid bleach.

 

[mknauss]

Be aware that the low pH that damaged the pool plaster was also damaging the heater. Expect that to fail in the not too distant future.

 

[Exlonghorn]

Funny that you said that...I started having a heater problem about a month ago...not sure if it's related. It will light and the burners will ignite for about 10 seconds and then go out. It will retry this cycle 3-4 times and then error out. The manual suggests something is wrong with the ignition circuit (CHECK IGN CONTROL error indicating an issue with the igniter, flame sensor, gas valve, or ignition control).

Retested just now to run an OCLT tonight. Will perform a full spread of tests in the morning. The good news is that I don't think the water has looked this good before (it's usually good, but this looks perfectly clear)
FC = 11.2
CC= 0.2-0.4 (it rained this afternoon, so that might be behind the small increase)
TA=130
pH=7.4