Salt and Calcium Hardness both Unexpectedly HIGH!

[panamax53]

The last time I added salt and calcium was almost 7 months ago in October 2016. At the time my CH was 375 and my salt was 4200.
I have not had to drain water from the pool since then.
I test frequently for FC and pH. TA and CYA get checked monthly. I figured I could forget about CH and Salt frequent testing since I did not have to really drain the pool in the winter season. Assuming the CH of 375 and Na Cl reading of 4200 were correct way back then and neither Salt nor Calcium have been added since, how could these two have increased?
I noticed increasing need to acid wash my SWCG plates. That was a hint. I noticed over the last two months I needed to jump my acid additon from 6 oz to 10 oz. Another hint I missed?
I see no visible signs of scaling. My latest test, today gave me FC 5, pH 7.7, TA 50, NaCL 5200, CH 550. Pool is clean and sparkling. I have only needed to add water from the hose. that water's CH is 25-50.
I was very surprised to find the increase in those two chemicals.
Before I drain 25% of my pool water and flush a lot of chemicals down the drain, does anyone have any ideas or suggestions?
Thanks

 

[Patrick_B]

You can't assume the salt reading was correct. Are you using a Salt test kit for the latest reading you got? The CH can easily increase through evaporation and refill, and how fast depends on your makeup water content. What is your makeup water CH? Through that in, and a little testing variation, evaporation, and voila! Also, have you added any Chlorine source with Calcium in it? That can add as well. Not surprising really, depending on what all is going on.

 

[panamax53]

Test Kit same as signature. Salt test done at home, in store and w new chemicals. I failed to realize the calcium increase could happen in dry season depending on how often I have to fill. Gotta check CH more often. Salt increase still inexplicable. All liquid or SWG created bleach.