I have a 3000 gallon plaster pool with a SWCG and a bluestone waterline tile (sealed) that has now been in service for 15 months. I was not too surprised that the pH would rise quickly during the time the the plaster is curing, but nothing has changed after 18 months.
I've recently tried going with a higher CYA (80 instead of 50) and managed to get the SWCG down to 6%. at this setting, the pH will rise from 7.0 to 8.0 in 2.5 days. Even with the SWCG off and using tricolor (because it will not raise the pH) for sanitizer, the pH will rise from 7.0 to 8.0 in 4-5 days. i've considered adding borax, which might help a little bit, but I really want to figure out what the heck is causing the ph to rise.
This link has a spreadsheet of what has been going on with the pool chemistry over the past few weeks Pool chemistry - Google Sheets. Like I stated, this problem has been going on since the pool was put into service, but I'm finally trying to get some answers as the plaster should have cured by now. Any help is greatly appreciated.