Would like to reduce 200-250 CYA in an ~15000gallon in ground pebble tec pool.
recommendation for digital water tester.
recommendation for digital water tester.
Due to your location, you may find a Reverse Osmosis service in your area. As stated, the enzyme additives have not been very successful. Sadly, that leaves you the only option: a (partial) drain and refill.
If you haven't already hit Pool School, you should..... at least that will explain in detail how you got such an astronomical CYA and how to prevent that from ever reoccurring.
Cavery, please delve into reading the Pool School articles above about desired pool chemistry levels. CYA of 150 and CH of 500 is too high. Please start with this article-
Pool School - Recommended Levels
Your only other option is to used only Cal Hypo shock to chlorinate your pool, it will come down slowly over time. There are also slow dissolving Cal-Hypo tabs that can be put into the skimmer in place of regular tri-chlor tabs.