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Thread: Pool Math has FC, but I'm using Bromine. Converting with 2.25

  1. Back To Top    #1

    Join Date
    Mar 2015
    Huntington Beach, California

    Pool Math has FC, but I'm using Bromine. Converting with 2.25

    I can never seem to find this conversion number so I'm putting it here.

    Taylor K-2106 tests for Total Bromine. Pool Math doesn't have a Bromine area. It has Free Chlorine (FC). The conversion is with 2.25.

    I use the K-2106 kit and test for Total Bromine (Br-), pH, Total Alkalinity (TA), Calcium Hardness (CH).

    Then, I head down to the bottom of Pool Math to the "Suggested Goal Levels" area and select "Traditional Spa".

    I make sure I have the correct gallons and temperature entered.

    I'm using Borates, so I enter 50 in both Now and Target since I set it and forget it.

    I type in my pH, TA, and CH "Now" measurements, noting that there is no Total Bromine area. Pool Math has Free Chlorine (FC).

    After selecting Traditional Spa, the FC area will show "Goal: 1 to 6" This gets a little confusing, because those numbers are good goals for a spa, either Bromine or Free Chlorine, but those numbers don't affect the automatic calculator portion of Pool Math. They're just telling you that if you you're on Chlorine, aim for those numbers. However, you will mess up your Bromine settings in your spa if you ignored the fact that the numbers that you have to enter into Pool Math must be FC, not Total Bromine that your K-2106 test kit will show you after doing a Total Bromine Test. You have to convert your Total Bromine findings by dividing Total Bromine by 2.25.


    I test with Taylor K-2106 and my spa's Total Bromine result is 0.5 ppm. But, what I really want is 2.0 ppm Total Bromine. Since Pool Math only has FC area, I have to convert with 2.25 so I can tell it FC.

    0.5 / 2.25 = .222 (I enter .222 into Pool Math, FC, "Now" box)

    2.0 / 2.25 = .889 (I enter .889 into Pool Math, FC, "Target" box)

    Then, since the Bleach that I am using is 8.25% concentration, I type "8.25" in the box next to "weight" % bleach.Jug size..."

    The result I am looking for is the "Add ?.? oz" (to the left of my bleach percentage). This number automatically gets calculated and will change based on the Now, Target, and % bleach number you provide.

    In my example, with a Now of .222 and Target of .889 and 8.25% bleach, it shows "Add 0.4 oz of 8.25 weight % bleach. Jug size ??? (jug size doesn't matter)"

    If I mouse over the "Add 0.4 oz", I will see "2 tsp" pop up in the "Mouse over a field for detail" white box at the top. This lets you know that 0.4 oz is the same as 2 teaspoons.

    I then go add 2 teaspoons of 8.25% bleach to my hottub to raise the Total Bromine level from 0.5 ppm to 2.0 ppm.

    Screen Shot 2016-02-21 at 8.00.37 AM.jpg
    Last edited by heykerrdog; 02-21-2016 at 11:23 AM. Reason: typos
    2007 Artesian Island Spa, Bahama 52, 2 pump, 450 gallon, Serial# 75777, Build date 2/23/2007, on Bromine and Borates.

  2. Back To Top    #2
    Mod Squad Texas Splash's Avatar
    Join Date
    Jun 2014
    South-Central Texas, Marion/San Antonio

    Re: Pool Math has FC, but I'm using Bromine. Converting with 2.25

    I've seen the conversion buried in some other posts like HERE, but can be difficult to find at times. Some threads get very lengthy. Your illustration reads well and I came-up with the same numbers.
    Pat (a.k.a. Texas Splash) ~ My Pool: Viking Fiberglass; 17,888 Gal; Waterway Supreme 2-sp/2-hp pump; Hayward Ctg filter; TF-100 w/ Speed Stir
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