[Doug Huffman]

I am a long retired nuclear engineering technician/engineer with just enough chemistry background to supervise and approve analyses and additions.  I live on a small rural Island in Lake Michigan and so have to make do with resources available here and on the 'net.  Thanks in advance for any assistance.

I recently installed a hot tub to reduce the volume of wastewater sent to my holding tank, from bathing, for disposal.  To operate it as frugally as possible I have just installed a buffer solution to obviate the need to chase the specified pH and 'Total Alkalinity'. 

The Association of Pool and Spa Professionals recommend 'Calcium Hardness' as CaCO3 150 - 250 ppm; 'Total Alkalinity' 100 - 120 ppm;  pH 7.4 - 7.6; and total Bromine 2.0 - 4.0 ppm

I analyze using Taylor Technologies Kit K-2005. 

http://www.taylortechnologies.com/products_kitinfo.asp?&MarketID=1&KitID=2227

I have some confidence in my results, but have not purchased or used their standards kit.

The buffer is boric acid and sodium carbonate in proportions for an indicated 7.5 pH, about 95.8% boric acid to 4.2% sodium carbonate in 225 gallons.  I added 400 grams total using a digital kitchen scale that can indicate in 0.5 gram increments. 

The initial pH was 7.0 and required 12 drops of Taylor's 'base demand reagent'.  Fortunately Taylor's 'Pool & Spa Water Chemistry' (PN #2004B) Table D shows mass of NaCO3 to raise pH by drop count of the reagent.  I added 46.0 grams indicated of NaCO3 for a final indicated pH of 7.5.  Success!

Now the question; what resources might I have or can I get to indicate the boric acid mass addition to lower pH?

I'll answer what questions I can and await your interest.  doug.huffman@wildblue.net

[Dietitian]

I am a long retired nuclear engineering technician/engineer with just enough chemistry background to supervise and approve analyses and additions.  I live on a small rural Island in Lake Michigan and so have to make do with resources available here and on the 'net.  Thanks in advance for any assistance.

I recently installed a hot tub to reduce the volume of wastewater sent to my holding tank, from bathing, for disposal.  To operate it as frugally as possible I have just installed a buffer solution to obviate the need to chase the specified pH and 'Total Alkalinity'. 

The Association of Pool and Spa Professionals recommend 'Calcium Hardness' as CaCO3 150 - 250 ppm; 'Total Alkalinity' 100 - 120 ppm;  pH 7.4 - 7.6; and total Bromine 2.0 - 4.0 ppm

I analyze using Taylor Technologies Kit K-2005. 

http://www.taylortechnologies.com/products_kitinfo.asp?&MarketID=1&KitID=2227

I have some confidence in my results, but have not purchased or used their standards kit.

The buffer is boric acid and sodium carbonate in proportions for an indicated 7.5 pH, about 95.8% boric acid to 4.2% sodium carbonate in 225 gallons.  I added 400 grams total using a digital kitchen scale that can indicate in 0.5 gram increments. 

The initial pH was 7.0 and required 12 drops of Taylor's 'base demand reagent'.  Fortunately Taylor's 'Pool & Spa Water Chemistry' (PN #2004B) Table D shows mass of NaCO3 to raise pH by drop count of the reagent.  I added 46.0 grams indicated of NaCO3 for a final indicated pH of 7.5.  Success!

Now the question; what resources might I have or can I get to indicate the boric acid mass addition to lower pH?

I'll answer what questions I can and await your interest.  doug.huffman@wildblue.net

You can use The Pool Calculator:

http://www.poolcalculator.com/

It is also available for the iPhone.  I use it to balance my hot tub and it allows for boric acid or borax as a borate source.

http://itunes.apple.com/app/pool-calculator/id309449280?mt=8