We just got a ton of rain from the remnants of Harvey and I had to drain a bunch of water to keep the level in my inground fiberglass pool below the top of the skimmers last night. I cleaned the pool this morning and let everything circulate for a few hours and then decided to test all the chemicals with the TF 100 kit. Calcium hardness just dropped a little, TA stayed roughly the same. Chlorine and pH weren't off much either (pool is SWCG). However, my CYA was up to 90. Last I checked before the rain(could of weeks ago was 70. Can rain make CYA go up or is there anything that can throw this test off? It normally isn't a very cloudy solution, but this one was today.