My fill water has a calcium hardness of ~400. It also has a TA of around 225. I filled my hot tub, and have been adding muriatic acid to lower the TA. While I've been adding the MA, I have lowered the TA to 130 but now the CH reads 25? Is this possible? I've been adding the MA until my pH gets around 7.1 and then adding when it reaches 7.8, it is dropping the TA, but I did not realize it would lower the CH like it has to this extreme. Checked it twice with my TF100 kit.
PS: I should add I also added 1800 ppm salt. I still do not understand how the CH could go from ~400 to 25
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