Weeks ago, my CH registered at 250. Today it registered at 425. Obviously I want to get it back in the normal range of 250-350. I'm wondering what is causing this gradual rise. Are there other chemicals (I'm using the BBB method) that is causing this rise? Can CH be impacted by water temp changes ie. low to high? My outside source water is at 300 (originally filled using home water filtration) which measured at 25ppm. Pool was drained to about 40%, then refilled. That's how I started at 250. I haven't added much water since it originally checked at 250. Any assistance is appreciated.