Which chem to increase ph?

I've accidentally added a bit too much acid to my pool and brought ph down to 7.0. I've never had to add anything to increase ph before (usually it's regular addition of acid to decrease) and in reading the guides I see a little bit of conflicting (or more like confusing) information on increasing ph.

Should I be using sodium carbonate or sodium tetraborate to increase ph?

Also, I had planned to let the kids go swimming this afternoon; should I not let them swim until I've raised the ph back up?

Well, you have a couple of approaches, and which is best depends on your other measurements.

Let's say, just for argument's sake, all your other levels are fine. 7.0 is a LITTLE low, but the kids in the water are going to do a lot of splashing (that is, if they are kids, and are having fun!) This is a GOOD THING because it will aerate your water and that action actually raises pH. If they are splashing like young dolphins and seals for 2 hours, your pH will go up! (but your total alkalinity won't).

OTOH, let's say, all your chems are fine except your Total Alkalinity is very low (say, below 60 or less, or even 70ppm) Then adding Soda Ash, aka, Sodium Carbonate (Arm&Hammer Washing Soda, in the YELLOW box, not orange) will raise pH and T/A rather quickly. You could also use Sodium Tetraborate (20 Mule Team Borax) to raise pH. Since T/A changes with pH, it will rise, too, but not as much as from Sodium Carbonate.

Now I'm making the HUGE assumption that all your other levels are OK and safe.

What would I do? Personally, I'd add just enough Borax to raise pH to anywhere between 7.2 and 7.4, and, when it's there, toss in the kids.

But, ultimately, it's up to you. We can only give you our best guesses and estimates. The final decision is yours.

Thanks Looks like the kids swimming did it. As quickly as ph rises in my pool I think I'm going to skip the borax, maybe I'll get 2 weeks without having to add acid instead of one!

Other readings btw:

FC: 14.0
CC: 0
CYA: 60
PH: 7.2 (after the kids)
Alk: 100
CH: 270