Boric acid?

[mx702]

Awaiting delivery on a new tub and I am looking to add borates to my water after balancing. I prefer to use boric acid rather that the borax/MA method. Where have you folks had luck finding the stuff?

I see the local big box stores carry roach killing powder which according to the MSDS is 99% orthoboric acid. Would this suffice?

 

[JamesW]

Here are some suppliers.

http://www.chemistrystore.com/search.cg ... boric+acid

http://www.dudadiesel.com/search.php?query=boric

 

[chem geek]

I see the local big box stores carry roach killing powder which according to the MSDS is 99% orthoboric acid. Would this suffice?

Yes, orthoboric acid is the same as boric acid. Though it should work, you're probably better off getting the pure stuff from the links James provided unless you are sure that the 1% in the roach killing powder is inert and not some sort of additional chemical that you wouldn't want to put into your pool. It might be fine as an alternative product just as Arm & Hammer Baking Soda and 20 Mule Team Borax are fine and pure enough for what they do, but I can't vouch for the product you describe specifically.

You can also get boric acid in spa products such as ProTeam® Gentle Spa. It is also in larger quantities in ProTeam® Supreme PLUS though is generally more expensive than the online sources linked to above (just remember to add the substantial shipping charges when making comparisons).

 

[mx702]

Thanks for the responses and links.

Am I correct in assuming that straight boric acid is relatively pH neutral like the Gentle Spa products?

 

[JamesW]

Boric acid is mostly pH neutral. It will slightly lower the pH, depending on the starting pH.

For example, at a starting pH of 7.6, the pH will be lowered by about 0.18 to about 7.42. You could add 48.6 ppm from boric acid and 1.4 ppm from Borax to get exact pH neutrality (assuming a starting pH of 7.6).

Also, the effect is self-limiting. The lower the starting pH, the less effect the boric acid will have on the pH.

For example, at a starting pH of 7.2, adding 50 ppm boron from boric acid will only lower the pH by 0.06. So, from 7.2 to 7.14.

Since the tub will need to be periodically drained and refilled, you could get about 5 to 7 pounds so that you have enough to redo the borates as needed. A 420 gallon tub will take 1 pound of boric acid.

 

[svenpup]

Another strike against the roach powder is the fact that it is powder. When I did mine I got some of the granular and some of the powder to see which was better. The powder floated on top of the water, blew around, and was a general pain to get to dissolve.