My understanding is that for our pool CH should be between 350 and 450. Measured CH has been dropping. On 7/13/2020, CH = 380. On 7/31/2020, CH = 330. On 8/17/2020, CH = 320. Is CH = 320 a problem? If so, what should I do? Thank you.
Not really a problem. Your CH is measured along with the pH, TA, and water temp to determine how aggressive the water might be (erosion) or how hard (scale) - hence the CSI rating on the PoolMath APP. You are still within acceptable ranges, so nothing to take action for at this time.
It is odd that the CH is dropping though. What about your CYA or salt levels? Those three items generally fall from changing water .... or a leak. No chance of that I hope?