chlorine mixing Q's

[PBLsQuad450]

Thanks CarlD- I checked first on-line and yep, they are identical. Same price too.

Watermom- Thanks for the reply. I'm not sure why bleach doesn't drive up the ph more? But hey, I liked chemistry so much in high school I took it twice. Same class! Passed with a "C" the 2nd time!

Funny in a sense that people kind of wish they had been "badder." The stats go accross cultural and class lines too.

PF rocks! If I am grasping this, then it is a miracle. Just bought ~15 pounds of 20 Mule Team Borax for $9.00. When I was at Leslie geting the test kit I priced Soda Ash. For 15 lbs. it was $30.00.

[Watermom]

Yeah, you got it. plus Borax will only raise your pH and not mess with your alk. Soda ash will do both. So, if your alk is fine and your pH is low and you add soda ash, then you gotta go back to the store and buy something to lower your alk back down to where it already was and then that new addtion will cause your pH to drop so you gotta go back and buy some pH up and then.............. while the cash registers go 'cha-ching!'

[CarlD]

Caveat:

Watermom is, of course, correct that Borax will not mess with your T/A.

HOWEVER, you must understand that pH and T/A are linked and when pH goes up, T/A goes up, and when pH goes down, T/A goes down. The ONLY way to raise pH without raising T/A is by aeration--fountains, splashing kids, etc.

So, in this vein, if you use soda ash (Washing Soda) your pH will go up but so will your T/A. If you were to lower you pH to back where you started, your T/A would be higher than when you started.

[chem geek]

I'm not sure why bleach doesn't drive up the ph more?

The short answer that explains this seeming conundrum is that though the pH does rise when you add bleach (or any other hypohchlorite source of chlorine such as chlorinating liquid, Cal-Hypo, or lithium hypochlorite), the pH falls back down again when the chlorine gets used up -- that is, when the Free Chlorine (FC) drops back down. This is because the consumption/usage of chlorine is an acidic process that balances out the initial rise in pH from the chlorine addition. I explain this technically in this post, but that's chemistry that will probably cause you nightmares so avert your eyes if you accidentally click on the link.

The only net pH rise will be from the "excess lye" that is added to bleach and chlorinating liquid (and less so with Cal-Hypo), but this amount is low in high quality bleach products like 6% Clorox Regular unscented which has a pH of 11.9 and in high-quality chlorinating liquid that has a pH of 12.5. There are many off-brand 6% Ultra bleach products that have more excess lye in them and have a pH of 12.5, 13 or more and would tend to have the pH rise more quickly.

There is also a tendency for pH to rise in pools due to carbon dioxide outgassing, but this can be minimized by keeping the TA lower. Finally, the pH can rise substantially in newly plastered pools due to the curing of plaster.

Richard