1. ## Thanks TFP!

Hey TFP, just taking a few minutes of unproductive work time and putting it back into the TFP community.

Love the site, helped me out a lot in pointing out the right direction such as getting a professional test kit. I just wanted to give other people insight to what I found. Blue devil has a good kit (with Alkalinity, calcium harness and CYA tests) but no FAS-DPD, and at first look, I kept debating to shelling out 20 bucks just for the FAS-DPD if it was worth it. what I found is that FAS-DPD is definitely needed when you have problems (ie algae) and need to get the right chlorine shock value. So shell out the extra bucks to get the complete kit.

Second The pool math is a good tool, but I don't think it can calculate precisely the amount of chemicals (because possibly it doesn't account for all the minerals differences in the pool and their effect on chemistry).
What I found the best thing to do is to use the pool math tool to get an initial number and then to test all your water in a 2 gallon bucket as a control test sample, rather than "dump and pray" in your pool which is a big waste of time and chemicals.
I found that my pool actually takes 2x the amount of muriatic and 3x the amount of chlorine to move the needle compared to the pool math calculator.

Note on alkalinity: According to EPA, alkalinity is the water's resistance change to acid. I loaded the alkalinity in my 2 gallon bucket to 300ppm, and reduced the acidity to 7.2ph. Within a fortnight the PH was back above 8.2. My alkalinity in my pool stands at 60-80, and is very consistent when I reduce it to 7.2-7.4ph. My conclusion here is that, if you have an algae problem, to get the maximum effect of chlorine, you would have to lower your alkalinity to maintain a low ph. There's a good corrosion to PH chart that should be referenced to. Although at 60-80 ppm 7.2 ph is technically corrosive (however minor), it is the best way to kill algae, and once that's done, I would probably bring my alkalinity back to 125 and keep my ph at 7.5 (neutral). Tip here is to downloading this graph (available on the net). So tip here is to adjust alkalinity as needed rather than "keep it at ideal alkalinity"

You can also get more use out of the test kit by halving the amount of chemicals used and halving the water amount. (duh right?) Readings by 1ppm is the same as .5, and readings by 20 ppm alkalinity.

That's my tips and findings so far, but more to play.

2. ## Re: Thanks TFP!

"rather than "dump and pray" in your pool which is a big waste of time and chemicals."

Just maybe the number of gallons you're dosing for may be off. Experience shows me that PoolMath is pretty much on the money.

Off by 2x and 3x on MA and chlorine is poppycock.

3. ## Re: Thanks TFP!

^^^^^

I'll second that. PoolMath is always spot on when I use it.

4. ## Re: Thanks TFP!

While there are certainly variables PoolMath does not take into consideration, I find it hard to believe that it can be off 100-200% as that would make PoolMath completely useless.

More likely, [OP], is that you aren't inputting the parameters correctly such as maybe you are using 14.5% MA and in PoolMath you are using the 31.45% value. I can see how you would need to 2x, 100%, or double the amount then.

5. ## Re: Thanks TFP!

PoolMath has been frighting accurate for me

6. ## Re: Thanks TFP!

That's definitely strange, i'm not ruling out anything, including my own errors. I just started, so I'm still playing with the numbers.

7. ## Re: Thanks TFP!

Originally Posted by jonnyrockt
Second The pool math is a good tool, but I don't think it can calculate precisely the amount of chemicals (because possibly it doesn't account for all the minerals differences in the pool and their effect on chemistry).
What I found the best thing to do is to use the pool math tool to get an initial number and then to test all your water in a 2 gallon bucket as a control test sample, rather than "dump and pray" in your pool which is a big waste of time and chemicals.
I found that my pool actually takes 2x the amount of muriatic and 3x the amount of chlorine to move the needle compared to the pool math calculator.
The chlorine calculation is correct so either your gallons are off or your chlorine isn't as strong as you think or you tested too long after you added it or too soon before it mixed.

The pH calculations can be approximate if one is outside normal ranges, but the pH does take into account the pH buffers of TA, CYA, and Borates if you enter them into PoolMath. I'm talking about the upper section where you enter pH and it tells you how much to add. The "Effects of adding chemicals" section does not use the TA, CYA, and Borates data so is more approximate. I suspect that your pH estimate was off a bit -- it doesn't take much especially at lower pH to have the amount of pH adjustment chemicals needed be quite a bit different.

Originally Posted by jonnyrockt
Note on alkalinity: According to EPA, alkalinity is the water's resistance change to acid. I loaded the alkalinity in my 2 gallon bucket to 300ppm, and reduced the acidity to 7.2ph. Within a fortnight the PH was back above 8.2. My alkalinity in my pool stands at 60-80, and is very consistent when I reduce it to 7.2-7.4ph. My conclusion here is that, if you have an algae problem, to get the maximum effect of chlorine, you would have to lower your alkalinity to maintain a low ph. There's a good corrosion to PH chart that should be referenced to. Although at 60-80 ppm 7.2 ph is technically corrosive (however minor), it is the best way to kill algae, and once that's done, I would probably bring my alkalinity back to 125 and keep my ph at 7.5 (neutral). Tip here is to downloading this graph (available on the net). So tip here is to adjust alkalinity as needed rather than "keep it at ideal alkalinity"
TA is NOT just water's resistance to change from acid addition. TA is a SOURCE of rising pH in its own right because TA is mostly a measure of how over-carbonated the water is with respect to air. So a higher TA level will usually outgas carbon dioxide faster and have the pH rise faster as a result and is most noticeable when using hypochlorite sources of chlorine because they are close to net pH neutral when accounting for chlorine usage/consumption. This is why you saw the pH rise so quickly in the bucket with high TA -- also the bucket is shallow so the outgassing affects the water more (i.e. more surface area compared to volume of water).

However, this has nothing at all to do with being "the best way to kill algae". You do not need your pH lower to kill algae. You only need your FC/CYA ratio to be high enough. The active chlorine level does not change with pH very much when CYA is present because CYA acts as an active chlorine (hypochlorous acid) buffer. Again, you need to stop reading other sources that are either incomplete or incorrect.

Originally Posted by jonnyrockt
You can also get more use out of the test kit by halving the amount of chemicals used and halving the water amount. (duh right?) Readings by 1ppm is the same as .5, and readings by 20 ppm alkalinity.
I wouldn't use a 5 ml water sample for most tests. If you knew your CH was very high, then perhaps for that test the 50 ppm resolution would be OK, but in general the 25 ppm resolution is reasonable and for TA 10 ppm resolution is reasonable. For FC, you usually need 0.5 ppm resolution unless your FC level is high (as with higher CYA levels). It's not just the resolution that gets broader with a 5 ml water sample, but your error is doubled in your measurement of that 5 ml sample. If your error is +/- 0.5 ml, then that's a 10% error with a 5 ml water sample but it's only a 5% error with a 10 ml water sample.

8. ## Re: Thanks TFP!

I too have never had a problem with Pool Math, as long as, I, myself, put in the correct numbers. I have found it to be a very beneficial, and absolutely necessary tool while SLAMming, and maintaining my pool. The ability to be able to plug in my current number, target number, add the amount of whatever chemical that the Pool Math calculator tells me to add, and then have that chemical addition sit my level right on top of my target number, as anticipated, has been nothing but unbelievably accurate.

9. ## Re: Thanks TFP!

Chem-Geek,

Appreciate the detailed inputs.

So, last night I retested everything. Since I'm using a 2 gallon sample, the size of water is constant. I also measured the pool size again and it's 8 feet by 25.5, with a small circular (4.5 radius). The gallons came out roughly 7000 gallons. Using the pool math, from FC 12 to FC18 with a cya of 45, it required 54 oz of chlorine @ 10%. Also, I tested the strength of Chlorine by diluting a 100ml and 100ml sample and the drop test came out 10 drops. exactly 10%. So the strength of chlorine is ruled out. 54 oz of chlorine divided by 3500 is .0154 oz, times 29.5 is approx .454 or lets say .5 ML. I ended up using 1ML of chlorine to achieve the FC18. Thats 2x. my original thread stated 3x, (but discount the enthusiasm of my discovery)
So I stand by the calculations. Granted there is a decent margin of error of at least 5-20%.
Taking this to my real pool, I dumped starting with FC12 I dumped in approximately 250 oz of 10% chlorine and achieved an FC23. I did that because the required amount of 107oz x (twice the amount). I'm trying to get rid of yellow algae btw (just a little on the walls)

So both the sample and practical outputs agreed. My alkaline as mentioned before is about 80, PH is 7.8 as of this morning, CYA 45. As my original post hypothesized, the only thing I can think of is I have a calcium hardness of 500 which is more than twice the recommended amount (or the minerals in the water). I can only think that that is the issue. Unless there are other mineral factors or parameters that are unknown or untested for. I'm also in Vegas so the water is weird. I don't want to drain my pool this season. So I will test this hypothesis in my 2 gallon sample tonight by lowering the Calcium hardness. I can also only hypothesize that all the other posters achieved their results having their CH within 100-200, which would explain why everyone else pool math works spot on.

I'm using a Taylor Kit TF100 btw, since blue devils kit doesn't have FAS DPD so I didn't go with that. But another side note, There's a huge color spectrum of orange that the clorodotine plastic tube should cover. Not sure why any of the brands of OTO don't have those extra colors, perhaps just to sell their additional chemicals. I have noticed a big orange difference between 23PPM, and 12PPM and IT IS measurable.

There's plenty of sources with a chart showing effectiveness of chlorine and PH. And the Alkalinity definition is from the EPA (government) so I don't think the sources are the question. So you don't think there is any correlation of chlorine effectiveness with PH?

Without calibrated droppers and micro scales, so I think the margin of errors is irrelavent anyways for me. There's so much that's estimated, size of pool, amount of chems used. Anyways, I don't mind counting PPM by 1 rather than .5, alkalinity by 20 instead of 10 etc. At the rate i'm using the chemicals and testing, i need the extra tests!

10. ## Re: Thanks TFP!

A higher CH has nothing to do with chlorine and we have users with 1000+ ppm CH who don't have any mismatch with PoolMath calculations.

The 10% chlorinating liquid is in Trade % which means the % Available Chlorine by volume. In other words, in 1 gallon there is 0.1 gallon of equivalent 100% chlorine so is by definition 1 million ppm or the 1 gallon has 100,000 ppm FC. This is why adding 1 gallon to 10,000 gallons results in 100,000/10,000 = 10 ppm FC. 54 fluid ounces is 54/128 = 0.422 gallons so added to 10,000 gallons would be 0.422 * 10 = 4.22 ppm FC. In 7000 gallons it would be 4.22 * (10000/7000) = 6.03 ppm FC.

The government (EPA) doesn't know squat about the chlorine/CYA relationship nor even about the TA/pH relationship. You are going to have to decide who you believe about specific technical issues. The EPA is correct about TA being a pH buffer, but they are misleading in not telling you that TA is a SOURCE of rising pH. You can't mix advice here with that you read elsewhere. Instead, you can validate/verify what we write against the actual SCIENCE based on peer-reviewed scientific papers published in respected journals upon which we base our recommendations and the thousands upon thousands of real pools where such advice works as predicted. For example, the "plenty of sources with a chart showing effectiveness of chlorine and PH" do not take into account the presence of CYA which completely changes that relationship. As shown in the graphs in this post CYA buffers hypochlorous acid against changes in its concentration including those from changes in pH. Whereas the hypochlorous acid concentration drops by about 50% going from a pH of 7.5 to 8.0 if there is no CYA, it only drops by around 15% when CYA is present. The EPA and other sources didn't tell you that, did they? And yet you use them as a source of valid or complete information? Why?

11. ## Re: Thanks TFP!

7000 gallons = 54 oz
2 gallons = .0154oz

it's simple fractions.

12. ## Re: Thanks TFP!

To me, it sounds like the OP is trying to take shortcuts and its leading to errors. instead of questioning the accuracy of the tools/advice prepared by people with a lot more knowledge, I would look at what you are doing incorrectly.

- - - Updated - - -

Originally Posted by jonnyrockt
I'm trying to get rid of yellow algae btw (just a little on the walls)
there you go. that's why you are needing more chlorine than what pool math says. you have an algae outbreak, that consumes FC very quickly. that's why you are using more chlorine than what pool math says. the results in pool math do not take into account algae/organics that are quickly oxidizing your FC as soon as you put it in.

if you want to verify pool math, then use a larger sample size, and use clean tap water to test the effects.

what you should be doing right now instead of trying to debunk pool math is focus on SLAMing the pool and eliminating the algae.

13. ## Re: Thanks TFP!

It depends on how quickly one measures though. I wouldn't expect algae to use up that much chlorine that quickly unless we were talking about a lot of algae. Just some on the walls shouldn't do that. There's also loss during the day from sunlight, but again measuring soon after adding shouldn't be an issue. However, if one takes a bucket of water in the shade, one can see if the FC measures stable several times before adding chlorine and measuring again. I've done chlorine additions many times with not only the pool but also separate containers and it always comes out correctly. There is nothing wrong with the tool.

14. ## Re: Thanks TFP!

well when I see new people that say they have some algae on the walls, its usually more than that chemgeek most likely there is cloudy water that until you are TFP clear, they think its clear. we have no idea when he tested, etc. If he tested 45 min or an hour after adding bleach, well then im sure there could be some good losses. he is also using 5ml sample which maximizes the level of error thru testing as well as measuring out the 5.000ml

but we are in agreement, the pool math is correct.

15. ## Re: Thanks TFP!

Woah. Poster above, first of all, I am not trying to debunk the pool math. If that's what you both think i'm doing, either neither of you are reading my posts, and I can see why everyone here is up in arms. Just the opposite, the fact i'm basing all my research on pool math shows how much i use it. In fact, I see other people getting a little more overly emotional around here, and I don't think that's the way this community should offer people who are just putting new information on their pools here. If anything, that's what this site is all about right? DIY's who wants to figure it out. If it was simply BELIEVING someone, we should just all believe in the Pool store clerks. If thats what you got from the OP's email you should reread it more carefully.

I am experimenting and posting my results online - whether it's right or wrong is up for debate. If you can find the errors, point it out. So far I'm just getting rhetorics and all my numbers are wrong without any reason.

Second, you are assuming I had algae after I used pool math. I had algae problems before I even used pool math. I am using it now to get rid of the algae. So whether this affects the believability of my numbers or credibility above, that's up to you dude.

Anyways, if anyone else can point out other possibilities other than measurement errors, I'd welcome it.

16. ## Re: Thanks TFP!

when are you testing your FC after adding bleach? do your tests with the 10ml sample. if you have active algae, its not unheard of to lose half your FC in a couple of hours if you have an active algae bloom. we need more info.

17. ## Re: Thanks TFP!

OK, yes we (or at least I) thought you were saying that PoolMath was wrong. So I'm sorry to misinterpret what you were saying. If you are using that as a guide to something strange going on in your pool, well that's OK though you do have to be careful about measurement. It's not CH that's causing it. If you have unusual losses, then there is something like algae or fast oxidizing organics in the pool consuming chlorine, but if that were the case you should see the FC dropping even when not adding any.

I think rather than worrying about measurement errors now you first get the water stable. That is, get rid of the algae. So that means if you add chlorine, you measure sometime later, and it measures lower then you expect, add more chlorine. That doesn't mean PoolMath or even your measuring was wrong but rather that the chlorine is getting consumed fairly quickly. After you get to a stable point where the loss is just from sunlight so not that fast, then you can redo your experiments with that better water.

The "M" or Maintain part of a SLAM means doing whatever it takes to maintain the FC level. That means adding more chlorine if the FC drops. You don't need to worry about why so much, just keep the FC up.

18. ## Re: Thanks TFP!

Originally Posted by chem geek
A higher CH has nothing to do with chlorine and we have users with 1000+ ppm CH who don't have any mismatch with PoolMath calculations.

The 10% chlorinating liquid is in Trade % which means the % Available Chlorine by volume. In other words, in 1 gallon there is 0.1 gallon of equivalent 100% chlorine so is by definition 1 million ppm or the 1 gallon has 100,000 ppm FC. This is why adding 1 gallon to 10,000 gallons results in 100,000/10,000 = 10 ppm FC. 54 fluid ounces is 54/128 = 0.422 gallons so added to 10,000 gallons would be 0.422 * 10 = 4.22 ppm FC. In 7000 gallons it would be 4.22 * (10000/7000) = 6.03 ppm FC.

The government (EPA) doesn't know squat about the chlorine/CYA relationship nor even about the TA/pH relationship. You are going to have to decide who you believe about specific technical issues. The EPA is correct about TA being a pH buffer, but they are misleading in not telling you that TA is a SOURCE of rising pH. You can't mix advice here with that you read elsewhere. Instead, you can validate/verify what we write against the actual SCIENCE based on peer-reviewed scientific papers published in respected journals upon which we base our recommendations and the thousands upon thousands of real pools where such advice works as predicted. For example, the "plenty of sources with a chart showing effectiveness of chlorine and PH" do not take into account the presence of CYA which completely changes that relationship. As shown in the graphs in this post CYA buffers hypochlorous acid against changes in its concentration including those from changes in pH. Whereas the hypochlorous acid concentration drops by about 50% going from a pH of 7.5 to 8.0 if there is no CYA, it only drops by around 15% when CYA is present. The EPA and other sources didn't tell you that, did they? And yet you use them as a source of valid or complete information? Why?

Yes, I did that. But I had to add 1ML to get that 6ppm raise instead of the .5ML.

it was the same test, I was writing my original post from memory. Looking at my notes it was 2x. I already said i made a mistake writing that.

19. ## Re: Thanks TFP!

Originally Posted by jonnyrockt

Second, you are assuming I had algae after I used pool math. I had algae problems before I even used pool math. I am using it now to get rid of the algae.
that was my point, you have algae, which is consuming/oxidizing the chlorine. if you have visible algae, then you have a full blown algae outbreak. you can have algae even when you cant see it, can appear just as cloudy water. the fact that you have visible algae is the key. you are saying that the amount dictated by pool math is not accurate and you need 2-3 times that to get the required FC rise. my point is, pool math is assuming you do not have algae. you can add 10ppm of FC and it can be 0 in a couple of hours with a good algae bloom. that doesn't mean pool math is wrong, you hit the necessary FC amounts but by the time you checked it had lowered.

regarding your pH. are you testing your pH when your FC is at 10ppm or higher?? if so, the results are not accurate so adding muriatic acid to try and adjust it is not going to work. you can only test your pH when your FC is below 10ppm.

you will see many posts on here when people are battling algae about adding bleach, getting to say 15ppm right after, and then checking in 2 hours and its down to 2ppm.

- - - Updated - - -

Originally Posted by jonnyrockt
Woah. Poster above, first of all, I am not trying to debunk the pool math. If that's what you both think i'm doing, either neither of you are reading my posts, and I can see why everyone here is up in arms. .
go back and read your initial post again, I think you will see why we got that impression. believe me, I read it twice you say that its a good tool, but that you need 2-3x more MA and bleach than what pool math calculates. it insinuates that the pool calculator is wrong, which is flat out not true.

20. ## Re: Thanks TFP!

Originally Posted by chem geek
OK, yes we (or at least I) thought you were saying that PoolMath was wrong. So I'm sorry to misinterpret what you were saying. If you are using that as a guide to something strange going on in your pool, well that's OK though you do have to be careful about measurement. It's not CH that's causing it. If you have unusual losses, then there is something like algae or fast oxidizing organics in the pool consuming chlorine, but if that were the case you should see the FC dropping even when not adding any.

I think rather than worrying about measurement errors now you first get the water stable. That is, get rid of the algae. So that means if you add chlorine, you measure sometime later, and it measures lower then you expect, add more chlorine. That doesn't mean PoolMath or even your measuring was wrong but rather that the chlorine is getting consumed fairly quickly. After you get to a stable point where the loss is just from sunlight so not that fast, then you can redo your experiments with that better water.

The "M" or Maintain part of a SLAM means doing whatever it takes to maintain the FC level. That means adding more chlorine if the FC drops. You don't need to worry about why so much, just keep the FC up.
Sounds good, i'll get rid of the algae first and do the measurements again. It's a thin film of algae on the walls. It's not even a bloom....

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