Should rain screw up my numbers this much?

[waterbear]

In some localities the pH of rainwater can become very low (acid rain). This can lower both pH and TA but I don't think .5" of rain would have THAT much of an effect unless the rain was very corrosive and acidic! Is it possible that the rain washed something acidic into your pool?

[fishandfly]

Well guys, I searched the archives for info on adding borax. Understanding that the effect on ph was reliant upon the TA I added it in small dosages. Ended up adding just over 4 pounds (which was all I had). It rained a ton last night (likely an inch total) and testing today ended up with PH 7.2 and TA of 50.

I assume I should just continue to correct the ph with borax; then address the TA with baking soda. Is that correct?