Borax and dry acid

Apr 30, 2010
I'm working on Borating my spa, I find the pH is drifting high when I'm away for a week at a time, I turn the air off, but I assume this is normal due to aeration present just from the pump running? Also I guess the occasional bleach addition brings it up? I am also interested to see what effect it has on the somewhat intangible water "sparkle".
I have a Freeflow Solstice tub, it is listed as water capacity=340 gal. Is this the number I should be using to calculate volumes, or is this the volume to the brim, and it is always less than this?
I did manage to find some 20 Mule team Borax in a quite small local general store after being stumped by several big grocery stores. All I have to bring the pH back down is "Lo and Slo" from Spa Guard. I believe this is dry acid, but I'm not sure of this. I've got the Lamotte Borate test strips, for some reason I have yet to discover it was packaged with some Sulfuric acid reagent, but I don't see anywhere to use this as part of the test.
I've been reading the threads I can find, but still have a few questions.
Is my target 30 or 50ppm, (or anywhere in between)?
How much Borax to achieve this in the solstice?
How much lo and slo to bring PH back down?
What order should I add stuff in?
What will this be expected to do to my TA and CH?

I am of course asking late, since I already have done this: Added 200g of Borax, tested around 30 ppm borate I guess, test strips are a bit tough to read. pH was very high, at least 8. Added 150 g of lo and slo ( based on a rough guess from an acid demand test and the charts in the Taylor manual). I added it all at once, which was silly, as the pH went to 7.2, but I have just left it to aerate back up. I haven't had a chance to check TA or CH yet.

chem geek

TFP Expert
LifeTime Supporter
Mar 28, 2007
San Rafael, CA USA
Normally, it's much easier to buy boric acid or a product like ProTeam Gentle Spa which is pH balanced. Even though it's more expensive, the quantities used are low in a spa. If you use Borax plus acid, then you should add half the amount of each alternating and I would add the acid first so that you prevent scaling if your CH is high or metal staining if you have metal ions in the water (if your CH and metal ion content is very low, then adding the Borax first is OK).

I would target 50 ppm for the Borates.

Use The Pool Calculator to calculate dosages (be sure to put in your spa volume).

Your TA should only increase a small amount which may not be noticeable, around 5 ppm, after adding the Borates and adjusting the pH back to where you started. CH won't change at all.


LifeTime Supporter
Jan 11, 2009
Cupertino, CA
The Lo'n'Slo is dry acid (sodium bisulfate). I would use the 340 gallons as the volume at least to start with; if you find yourself constantly overdosing, then scale that down a bit.

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