# Spa Calculator for BBB?

#### Sabot

I am playing around with using BBB on my new Spa. I am also using the The Pool Calculator to help. I am dealing less water (325 gal), warmer water (94 to 99 degree water) and I keep my spa cover almost 23 hours a day. I am sure this impacts the numbers in the The Pool Calculator as well as the testing numbers.

I am wondering if anyone can come up with a Spa Calculator?

Thanks,
Mike

#### ktdave

You can try multiplying your spa volume by say, 10 (or 100). Input that number in the calculator (3250 or 32,500) and then divide the amount of chemical to add by 10 (or 100).

#### chem geek

TFP Expert
ktdave's suggestion is a good workaround.

[EDIT] Jason [END-EDIT], who wrote the calculator, can enhance it by adding smaller volumes for the chemicals in the "Mouse over a field for detail" when the result is small, such as a few ounces or less. He can use teaspoons as a converted measurement where there are 6 teaspoons in a fluid ounce and should show decimal amounts (as he does when in metric). Though there are 2 tablespoons in a fluid ounce and 3 teaspoons in a tablespoon, I don't think it's necessary to use tablespoons. Giving the number of teaspoons as a decimal, such as 2.3, is OK as I think most can convert from that to 1/4 or 1/3 teaspoon equivalents that are close.

Another alternative is to use the "Metric" mode of the Pool Calculator. The milliliters (ml) and grams (g) are small enough units to be precise even with small spa volumes. There are 29.57 milliliters in a fluid ounce -- easy enough to just use 30. So dividing the ml number by 30 gives you fluid ounces. Likewise, dividing by 4.93 (or roughly 5) gives you teaspoons. The density of most pool/spa chemicals is roughly 1 g/ml (and roughly 1 ounce weight / fluid ounce) though you can refer to this post to see typical "bulk" densities. So if you take the weight of the chemical (for dry chemicals) in grams and divide it by the density (g/ml) and then divide that by 5, you get how many teaspoons of chemical to add.

Richard

[EDIT] I corrected this post to say that Jason wrote the Pool Calculator, not Dave -- not sure where that come from but I've corrected this now. Thanks Rollin Thunder. [END-EDIT]

G

#### Guest

jasonlion wrote the calculator, pm, or (talk to him here) him if needed.

#### JasonLion

Platinum Supporter
TFP Expert
Providing more precision for smaller measurements sounds like a great idea. I will add that to the wish list for the next release. Hopefully I can get around to that soon, but just now I am very busy at work.

#### Sabot

Jason, I am using it for my spa as well. I was wondering if the higher temps and other factors found in a spa would require differant amounts of chems. I noticed on your calculator that you had water temp. It didn't seem to have a huge impact on the numbers.

#### chem geek

TFP Expert
Sabot,

The temperature only affects the Calcite Saturation Index. It does not affect anything else as far as chemical additions are concerned (i.e. how much acid or base to change pH or how much baking soda to increase TA, etc.). Essentially, calcium carbonate is more soluble in colder water -- the opposite of what happens with most other chemicals that tend to dissolve more readily in hotter water. So in a spa or hot tub that has grout exposed to the water or if it's a plaster spa, then you would use a lower Calcium Hardness (CH) and/or Total Alkalinity (TA) than you would in a pool.

Normally in most spas and hot tubs, they are not plaster and do not have tile with grout exposed to the water so normally the Calcium Hardness (CH) is kept low at 100-150 ppm (yet still high enough to prevent foaming) so you don't need to worry about the saturation index.

Richard