The last time I tested my pool water(January/February timeframe), the CH was hovering around ~200 to ~250ppm. When I got my TFTestkit refill, I immediately threw the old reagents away so as not to mix them with the new ones. But when I tested the CH last week and again today, it measured at ~425 to ~450ppm. This seems pretty drastic of a hike on measurement especially since we have not used the pool since September last year and our pool is covered with an automatic pool cover 99% of the time except for testing.
We've had some pretty heavy rains in Northern California (Bay Area) in January, but dry in February, then some rain in March - could this have caused the sudden rise in CH? Or was the older reagent not giving me correct results? The pool water is still around the vicinity of 55deg to 65deg F.
Also, the "Pool School - Recommended Levels" call for TA to be 70ppm to 90ppm for bleach. However, the chart from TFTestkits says 100ppm to 120ppm for manually chorinated pool - so which one to follow? My TA now is measuring ~125ppm (I was getting ~90 to ~100ppm using the older reagent - strange). Should I follow the Pool School recommended levels, or should I follow TFTestkits numbers?