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Thread: Calculating PPM by hand

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    Calculating PPM by hand

    Hey everyone! I know this site has a great calculator to determine how much chlorine to add to achieve a desired PPM, but I'd like to be able to calculate the same result by hand. According to Wiki (https://en.wikipedia.org/wiki/Parts-per_notation), .0001% = 1 PPM. Therefore, if I have 1,000 gallons (128,000 ounces) and add 1 TBSP (.5 ounce) of pure chlorine (as in 100% bleach, which I know doesn't exist publicly, just using it for easy calculations for now), I get 3.9 PPM (.5 divided by 128,000.5 = .0000039). If I input the same values, the calculator agrees perfectly.

    However, if we up the values significantly, the calculator no longer agrees. For example: With 50,000 gallons, to get to 4 PPM the calculator determines 25 ounces of pure chlorine. However, hand calculating is as follows: 50,000 gallons = 6,400,000 ounces. Add the 25 ounces for 6,400,025 total ounces. 25 divided by 6,400,025 = .0000039, or 3.9 PPM, not 4 PPM. Just to make sure the calculation simply doesn't include the added 25 ounces, 25 divided by 6,400,000 also equals 3.9 PPM. At first I thought maybe the calculator just rounded, but changing the desired level in the calculator to 3.9 changes the required ounces to 24. So, it's apparent I'm missing something here...

    Also, if that question can be answered, I haven't worked the math on substituting pure chlorine for the regularly available 5%, 6%, or 8.25% if anyone has a formula for that.

    As a final FYI, the only reason I'm trying to figure this out is to preserve the formula for occasions where technology is not readily available, such as natural disasters or winter storms. I know the page can be downloaded to the local computer, but if the power is out, it doesn't do much good.

    Thanks!
    Cam

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    mikemass's Avatar
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    Re: Calculating PPM by hand

    This Post ^^^ Is right up my alley. Subscribed!
    25 + year pool owner. Current pool (going on 11th year) - 38K gallon in ground Gunite/White Plaster, Spillover Spa, Hayward Cartridge Filter, Hayward 450k BTU NG Heater, Hayward Goldline Aqua Logic control with T-Cell-15 Salt Water Cell, Dolphin Explorer.
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    Re: Calculating PPM by hand

    Will there be a test and the end of this?
    Valley of the Sun, Arizona.....10k gunite/pebble (Re-surface March 2015) w/in floor Caretaker 99 cleaning heads -- Pentair FNS 60 DE filter -- Pentair IntelliFlo Variable Speed for pool -- Pentair Wisperflo 1 HP for boulder waterfall...Taylor K-2006 & Taylor K-2006C kits

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    Re: Calculating PPM by hand

    Cam - First question I have. If I go to pool Math page and enter 50k gallon pool, FC "now" of 0, and "Target" FC of 4.0 using 100% bleach, I get 60 ozs of bleach. Where are you getting 25 ozs?

    Once that is answered, then I am curious about the rounding aspect. But I will elaborate once we agree upon the amount of "100% bleach" to add to a 50k gallon pool.
    25 + year pool owner. Current pool (going on 11th year) - 38K gallon in ground Gunite/White Plaster, Spillover Spa, Hayward Cartridge Filter, Hayward 450k BTU NG Heater, Hayward Goldline Aqua Logic control with T-Cell-15 Salt Water Cell, Dolphin Explorer.
    You Need: Bleach, a A Test Kit & a Bookmark to "Pool School". Now what's your question?

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    Re: Calculating PPM by hand

    That is curious, here's a screen shot for proof of what I'm seeing:


    Capture.jpg

    - - - Updated - - -

    Well, it seems like someone has ripped off the calculator found on this site at poolcalculator.com, which is where the 25 ounces were coming from. Re-doing the math with the 60 ounces now...
    Attached Images Attached Images

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    Re: Calculating PPM by hand

    Quote Originally Posted by cdoc83 View Post
    That is curious, here's a screen shot for proof of what I'm seeing:

    Capture.jpg
    Well that just threw a wrench in things..... the updated page is this one:

    http://www.troublefreepool.com/calc.html

    pool math50k.jpg

    I think you are using the calculator from the Jason Lion Days of the forum.
    25 + year pool owner. Current pool (going on 11th year) - 38K gallon in ground Gunite/White Plaster, Spillover Spa, Hayward Cartridge Filter, Hayward 450k BTU NG Heater, Hayward Goldline Aqua Logic control with T-Cell-15 Salt Water Cell, Dolphin Explorer.
    You Need: Bleach, a A Test Kit & a Bookmark to "Pool School". Now what's your question?

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    Re: Calculating PPM by hand

    Sweet, thanks! Ok, using the calculator actually found on this site, it seems the math is worse... 50,000 gallons = 6,400,000 ounces, plus the 60 ounces of chlorine = 6,400,060 ounces. 60 ounces chlorine divided by 6,400,060 total ounces = .00000937, or 9.4 PPM. Now I'm more confused...

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    Re: Calculating PPM by hand

    No problem. Glad I caught that. But that is even more obscure now. The old vs new calculator is disagreeing by 150%. At least the old calculator was close to your hand calculation. (24 vs 25 ozs). But the new POOL MATH calculator is now a 1.5 times multiple of doing a hand calculation!!!! (24 vs 60 ozs).. You agree with that assessment right?
    25 + year pool owner. Current pool (going on 11th year) - 38K gallon in ground Gunite/White Plaster, Spillover Spa, Hayward Cartridge Filter, Hayward 450k BTU NG Heater, Hayward Goldline Aqua Logic control with T-Cell-15 Salt Water Cell, Dolphin Explorer.
    You Need: Bleach, a A Test Kit & a Bookmark to "Pool School". Now what's your question?

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    Re: Calculating PPM by hand

    Cam - Here's an interesting theory. Strictly theory. I'll lay it out there and perhaps you may see some credence in it:

    Being that there is no such thing as 100% bleach in real life, perhaps it is an unsolvable equation. But look at my snap shot above of the current POOL MATH calculator. There's an option in the drop down for "Chlorine Gas", which in theory should be 100% pure. (After all Chlorine is a gas as depicted in its placement on the Periodic Table of Elements.) But I digress....

    Back to the drop down in the menu. Notice that if you choose "chlorine gas" from the drop down, you do get 27ozs as your answer. At least this is closer to your 24 oz hand calculation.

    I know that's not an answer to this conundrum, but perhaps it can steer you in the right direction.
    25 + year pool owner. Current pool (going on 11th year) - 38K gallon in ground Gunite/White Plaster, Spillover Spa, Hayward Cartridge Filter, Hayward 450k BTU NG Heater, Hayward Goldline Aqua Logic control with T-Cell-15 Salt Water Cell, Dolphin Explorer.
    You Need: Bleach, a A Test Kit & a Bookmark to "Pool School". Now what's your question?

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    Re: Calculating PPM by hand

    Quote Originally Posted by cdoc83 View Post
    ................... As a final FYI, the only reason I'm trying to figure this out is to preserve the formula for occasions where technology is not readily available, such as natural disasters or winter storms. I know the page can be downloaded to the local computer, but if the power is out, it doesn't do much good.

    Thanks!
    Cam
    Welcome to the forum!

    While I'm a math & science nut, it's much easier to just use the "effects of adding chemicals" section of Pool Math.

    Once you enter your pool's volume up top, scroll down to the above mentioned section, pick a source of chlorine, and play with the amount until you get 1ppm.

    For instance, that works out for my pool at 7oz of 12.5%, 8.5oz of 10%, or 10oz of 8.25%. If I want to raise my FC 3ppm & I'm using 12.5% I just measure out 21oz of chlorine and add it to the pool, if it is still standing during said natural disaster, or not frozen over during said winter storm LOL.

    Easy Peasy.

    (I'd still be interested in any formulas though...)

    Dom
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    Re: Calculating PPM by hand

    My theory is that ya'll should do more swimming and less math!

    Have fun!
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    Re: Calculating PPM by hand

    Mike has hit on part of the issue. Try putting in 10% bleach and you get 256 oz., about 10 times your calculated value for 100% bleach. using 1% bleach gives 2616. not exactly linear, but in the ball park. note the changes in calculated ozs of bleach as you increase the bleach conc from 50 to 60 to 100. not linear at all. stick to typical ranges of actual bleach and you should be much closer to getting what you want.
    30000 gal inground vinyl liner;sand filter w/glass media, nuvo uv, TF-100 test kit; 25 years on Baquacil, converted to TFP chlorine in 2016

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    Re: Calculating PPM by hand

    Quote Originally Posted by mikemass View Post
    You agree with that assessment right?
    I agree with that assessment. I think I may have also found the potential "smoking gun" of the calculator being incorrect at values I'm trying to simulate. With the other values remaining constant, if I input 10% bleach solution into the calculator, it indicates 256 ounces is required. If I up the value to 20% bleach solution, the required ounces drops to 128 ounces as expected. However, 40% solution only drops to 68 ounces instead of the expected 64 ounces. Likewise 80% only drops to 49 ounces instead of the expected 34 ounces. It seems that right around 75% solution the required ounces bottom out and actually start to increase! There's definitely something wrong with the calculator...

    Given that anything above 20% is basically unattainable, I guess I can live with that =)

    Now to figure out the formula given the watered down nature of household bleach....

    - - - Updated - - -

    Quote Originally Posted by domct203 View Post
    ...if it is still standing during said natural disaster, or not frozen over during said winter storm LOL.
    Haha, I hear ya! I doubt I'd be worried about the pool at all... I guess a good portion of the drive to find a formula is the desire to not become reliant on technology. Kids these days can't write a simple email without asking Siri a dozen questions... =)

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    Re: Calculating PPM by hand

    Quote Originally Posted by cdoc83 View Post
    .........Haha, I hear ya! I doubt I'd be worried about the pool at all... I guess a good portion of the drive to find a formula is the desire to not become reliant on technology. Kids these days can't write a simple email without asking Siri a dozen questions... =)
    So, you know my daughters? LOL.

    Dom
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    Re: Calculating PPM by hand

    Alright, contacted a more science inclined friend, PPM, or parts per million, is actually a MASS ratio, not a VOLUME ratio... Water is commonly regarded as 1 gram per milliliter. Trying to see if we can find the mass of the chlorine part of the sodium hypochlorite....

    I'm starting to think pulling the javascript from the calculator might be easier...

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    Re: Calculating PPM by hand

    I'm with domct203 on this.

    I have a post-it note on the inside of my test kit listing how much it takes to raise FC 1ppm for the three most common bleach percentages (8.25, 10, 12.5) and for lowering pH by 0.1 using 31.45% MA for my pool volume.

    Two things I never have around the pool - anything glass and any portable electronic devices. Having either near my pool can have unpleasant results, to say the least.

    I think PoolMath is weighted for the most commonly available chlorine types and concentrations. PoolMath is kept up to date. I would certainly shy away from the Pool Calculator and it's associated app as it hasn't been updated in several years.
    Gene
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    Re: Calculating PPM by hand

    Quote Originally Posted by proavia View Post
    I have a post-it note on the inside of my test kit listing how much it takes to raise FC 1ppm for the three most common bleach percentages (8.25, 10, 12.5) and for lowering pH by 0.1 using 31.45% MA for my pool volume.
    Yeah, that totally makes sense. I'll probably leave it to that for now. Another part of figuring out a formula is to use it in other areas as well, such as creating the CDC recommended 200ppm solution for disinfecting after a flood or creating a 100ppm shock treatment for a cistern well, or whatever else may arise that I can't plan for

    Thanks all for the discussion, fun stuff!! I guess it's back to work for now...

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    Re: Calculating PPM by hand

    In case it's of any use for anyone else, here's the formula used by the calculator:

    ([Chlorine PPM Target] - [Current Chlorine PPM]) [Number of Gallons] {(75.71 [% of Bleach]) + (.746 [% of Bleach] [% of Bleach])}

    This formula was also verified by my science friend as "close enough" =) Enjoy!

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    Re: Calculating PPM by hand

    Someone posted a excel spreadsheet where you enter your pool gallons and it gives ozs of different percentage of LC to add for different PPMs. Cant remember where it was. I edited it printed it out and taped to the inside of my kit.
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    Re: Calculating PPM by hand

    Good grief.. all that math is giving me the willies!

    All I need to know is that 17 ounces of 8.25% bleach in my pool will raise my FC by 1ppm.
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