Ca Hardness Testing - Interpretation

28K GA / IG / Diamondbrite / SWC / DE filter
pH 7.4 / FC 5 / CC 0 / CYA 50 / Ca 220 / TA 100 / 87 degrees

My PS233 test kit readings of Ca hardness are consistently around 220. However, Leslies (200) and Warehouse Pool (180) are consistently lower. I know that Ca levels below 200 will harm my plaster and other equipment over time.

Questions:
1. Should I be confident that my PS233 Ca levels are more accurate than the pool store values? or could there be other factors that might cause my drop test results to be falsely elevated.
2. Should I consider adding a little CaCl2 to get my Ca up closer to 250 or 300 to protect my Diamondbrite?

Thanks in advance to any and all that can offer advice.

I would trust my own results with the PS233, but it won't hurt to bump the calcium up just a little and will probably give you peace of mind if you do.

Since your Ca is not dangerously low, you could use Calcium Hypochlorite for your chlorine source....it will slowly elevate your Ca and it's a pretty cheap source of chlorine