I used to get heartburn

from smoking too much especially drinking coffee and then again when I first started vaping. I was using the KR808 system and getting occasional mouthfuls of eliquid. I haven't really had it since I got my REO. Not sure if it's the REO or just adjustment after over 6 months of vaping.
I highly recommend Country Life Cal-Snack wafers as a natural antacid that works like Tums but less nasty chemicals. They are huge chewable vanilla/orange flavored wafers and you can drink water with them-very tasty. Heartburn goes away almost instantly. Usually one will do the trick and occasionally two if it's really bad. Technically they are Calcium with Magnesium and Vitamin D supplements, but they sure do the trick. A Whole Foods employee recommended them to me when I had a serious attack in the store. Don't buy them there though since they are over twice the price as buying online.
Since it feels like you are having a heart attack, instant relief is very reassuring. I've woken up with heartburn and been back to sleep in 5 minutes after eating one.