I am adding borates to my pool. All my local store had was 5 boxes of 20 mule team, so I decided to buy them and see how it tested afterwards (went from o borates to 15).
After I added them, my CH, which was testing at about 250, now tests at 450. I've looked high and low in the forums and on the web, and I don't see any warning or discussion of Borax driving up CH.
Before someone suggests it, I have been a pool owner for 20 years. I do my own testing with a Taylor 2005 kit (and an additional TFT FAS kit). I don't think it's in my test methods (but I've made mistakes before).
I really don't want to draw down the pool to lower the CH. I've been gradually getting the CYA where I want it through a slow addition of dry acid.
AFWIW, I will do the rest of the borate addition through boric acid, via DudaDeisel. This is the only way to go. Less of the boric product, and no hassle of Muriatic acid.