I have a 15000 gal inground pool and can not get PH up. Have put 3 4lb boxes of borax in it over a 3 day period and I am not getting much of a different reading.

Used bleach to open the pool and borax to adjust the PH.

Clorine is off the scale exceeding far above 3.0. Ph is well below 6.8. Alk is reading 100.

Using 3 inch tablets in an automatic Hayward Chlorinator and it is set on 1.

What is wrong?

Thank You