spring start up, general questions, BBB method

[chem geek]

CrisL is mostly correct, but I wanted to quantify some things. Technically, Borax or any base that raises pH will also raise the TA a little (just as any acid that lowers pH will also lower the TA a little), but it is true that it will not add carbonates to the pool and therefore will not raise the TA as much as pH Up (sodium carbonate / soda ash / washing soda). 1 pound of sodium carbonate in 10,000 gallons with your pH of 7.2 and TA of 80 will raise the pH to 7.48 and the TA to 91.3 while 1 pound of Borax will raise the pH to 7.33 and the TA to 83.1. For an equivalent rise in pH to 7.48, it takes 31.7 ounces (almost 2 pounds) of 20 Mule Team Borax and the TA will rise to 86.2, again per 10,000 gallons. So for the same pH rise it takes twice as much Borax by weight as sodium carbonate and the TA rises about half as much.

The reason for this is that Total Alkalinity includes the "alkalinity" from the difference of hydroxyl ions to hydrogen ions and this relationship is directly related to the pH. In some sense, the dissociated products of water itself act as a (very weak) pH buffer. The effect is small, but actually measurable in the TA test for larger changes in pH.

Richard