Are there any reasons not to use Borax to occasionally raise spa pH instead of soda ash?


Well-known member
Oct 4, 2018
I just re-started my tub after having it drained most of the summer. I got my TA down to 60, set Borate level at 40. and pH at 7.5. A few days after startup my pH had drifted down to 7.2 maybe in part due to the fact that I am chlorinating exclusively with dichlor until I get the CYA level up to 50. At that point, I will stop using dichlor and chlorinate pretty much exclusively with bleach. I understand that CYA levels taper off over time so once in awhile I'll use dichlor instead of bleach to maintain the CYA levels in the 40 - 50 ppm range over time.

With the pH at 7.2 I went on the old Pool Math calculator and figured out what my options were for raising pH back to 7.5. It seemed like my two best options were either to use soda ash/washing soda or borax. I noticed, however, that using the borax would only raise my TA by 4ppm whereas using Soda Ash would raise it by 10 which is less desirable given I try to keep my TA at around 60 ppm. The only downside of using the borax - if there really is one - is that the quantity of borax I'd need to adjust the pH upward by 0.3 would increase borate levels by 4 ppm so now the borate level would be 44 ppm instead of 40. Is that a problem?

The last time I ran that tub I also used the TFP system and I found that because I worked my TA down from about 150 to 60 ppm at startup, the pH remained very stable and I rarely had to do any pH adjustments either way. As such, I don't anticipate having to do many pH adjustments this time either so is there any reason why I shouldn't use borax instead of soda ash on the rare occasion where I have to bump the pH up a little? Is there a borate level I should be careful not to go above?

Bama Rambler

Mod Squad
TFP Expert
Bronze Supporter
LifeTime Supporter
Jun 22, 2009
SouthWest Alabama
There's no reason not to use Borax to raise the pH. The little bit that it raises the borate level shouldn't be an issue.

You shouldn't go above 80 ppm borates, but you're not likely to get close to that.