Please Help a newbie - Spa Ph Keeps on Rising

[fifoboy]

I did a full water change on my 350 gal Freeflow spa about a month ago, and since then I've had lots of trouble getting the Ph to stay in the right range, all of the other levels (TA, FC, CC, CH, CYA) all seem to behave, but the Ph just seems to stay at 8.0 and above.

Here are the supplies I'm using:

• Pool Pal android app for calculating how much to put in
  Taylor K2006 Test
  Standard Bleach and Dichlor (for the first couple of weeks)
  Baking Soda
  Calcium Chloride from the pool store
  Something Called "Ph Down" which seems to be dry acid
  Ph Minus from Spa Chem (haven't used this stuff but have a full bottle of it)

The Ph Down and Ph Minus products were left by the previous owner so I was hoping to use them up before buying Muratic acid.

I've been reading a lot of the info in Pool School, and in "How Do I use Chlorine" sticky post and I think I'm on the right path, but I'm not quite sure how I should proceed, so here is what I've done so far:

On Day 1:

• FC 4
  Ph ~8.0
  TA 80
  CH 110
  CYA 80

I added 10 grams of the Ph Down (aka Dry Acid), and aerated for about an hour and then:

• FC 4
  Ph 7.6
  TA 70
  CH 110
  CYA 80

I added about 8g more of dry acid and aerated 30 min and the readings stayed the same, so I thought things had stabilized, but then the next day:
Day 2

• FC 3
  Ph 8.0+
  TA 70
  CH 110
  CYA 80

So my question is: Do I add more acid to bring the Ph Down again, because it seems like if I do that I'll drop my TA too low and that will be bad or make the Ph levels very unstable (which I guess they already are)

Thanks for helping a newbie out!

 

[chem geek]

I would get the TA down to 50 ppm and then add 50 ppm Borates. Between the lower TA and the borates, the pH should be more stable, though with aeration from spa jets it may still rise somewhat. By the way, your CYA is higher than recommended for a spa. It should be more like 30 ppm or so (up to 50 ppm is probably OK, but 80 ppm is on the high side). The higher CYA level means that chlorine will take longer to oxidize bather waste so if you use the spa every day it's possible you won't be able to keep up. It will also make the chlorine less effective at killing bacteria, though not as problematic as those who use Dichlor-only and have their CYA get to 200 ppm or more in the last month or so before a water change (which is why one gets dull water and changes it sooner when using Dichlor-only).

 

[fifoboy]

Thanks for the advice. For borates, is it OK to go with Borax?, or would the Proteam Gentle Spa be a better choice?

As for the CYA, I started with Dichlor before I got my test kit in the mail and so by the time it arrived, I'd already overshot the the CYA. However, we typically aren't using the tub on a daily basis, maybe a few times a week. Is there any way short of a water change to bring the CYA level down?

 

[chem geek]

You can use Borax and acid if you want. I'd add the Borax first, then the acid, and I'd add half of each in two passes to avoid the possibility of scaling. If you lower your TA to 50 ppm first, then in a 350 gallon spa you would add 20.6 ounces weight (about 20 ounces volume so 2-1/2 cups) of 20 Mule Team Borax and 9.6 fluid ounces of full-strength Muriatic Acid (31.45% Hydrochloric Acid). Proteam Gentle Spa is supposed to be mostly boric acid so would be more convenient, but people have reported that it is no longer as pH-balanced as it is supposed to be. So it's up to you which to use.