Why would my ph keep going up?

It was high so the first week i added 1/2 gallon acid. It came down 8.2. Next week i added another 1/4 gallon and it came down to 8.0. Then i added another 1/4 gallon and it was down to 7.8....Now 2 weeks later it is back up to 8.2...

here are the other readings

total harness 100

total cl 3

free cl 4 (too high?)

ph 8.2

total alkalinity 123

cyanuric acid 100

I dont know the answer but my pool has also taken a sudden unexpected uptick in pH (treble its normal drift upwards). It rose from 7.3 to 7.85 in 17 days. I haven't tested the rainfall, but perhaps it is particularly alkaline right now (normally its slightly acidic)?

You seem to be aiming for quite a high pH level. Guidance I have seen suggests keeping the pool slightly acid - 7.2 to 7.4 to get maximum effectiveness from your chlorine. Perhaps that doesn't matter if you have a salt water chlorinator. I noted from another thread that Naam (who has decades of experience owning pools - not 18 months like me) goes for a pH target of 7.0* - but his is an indoor pool - dunno if that affects the target.

Also, your test result for Free Chlorine is higher than Total Chlorine. Again I'm no expert but I thought that Free Chlorine physically cannot be higher than Total Chlorine. {I wonder how you do a negative shock }

*Edit: but then I have now seen a posting by Curtklay who maintained pools in California for 25 years that the target ramge for pH is 7.4 to 7.6 (which is cocnsistent with the cheap dropper test kit guidance). I guess there are as many opinions on pools as there are experienced owners and professionals! Little wonder that us novice owners cast around a bit for a couple of years until we find our own levels.

pH can rise when using a saltwater chlorinator.