The ph did get high about 2.5 weeks ago when I went back to chlorinator - the adjustable valve evidently wasn't working right and we were on vacation a few days. It got up to around 15. My range is 3-6 on best guess chart based on my CYA. Since then, I have kept it in the 3.5 - 7.0 range. Through all this, the ph difference between the two kits have remained the same. There is a definite color difference depending on the kit. Hopes this answers your question.