Acid Demand and Borates

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Chad628

Chad628

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LifeTime Supporter
Jul 30, 2013
101
San Francisco Bay Area
About a year ago I added a quantity of 20 Mule Team Borax per pool math to my pool to raise my borates level to 50 ppm. I test the borates level with Lamotte test strips and get a reading between 50 and 80 parts per million. When i input a reading of 50 ppm borates in the pool calculator to arrive at the quantity of acid I need to reach my target ph level I get a result that is way too high resulting in lowering my ph to a level lower than my target level. I tried doing the Taylor acid demand test and the result of acid demand is much lower than what pool math suggests for borates of 50 ppm. When I play with the numbers in pool math it suggests that my borate levels are really 15 ppm based on the Taylor acid demand test.

Has anyone encountered this problem before?

Should I assume that the Lamotte test is not accurate and that in the last year my borate level has decreased by 35 ppm? Do borates get used up in the pool over time?

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Yes I did input my total alkalinity values. My test results this morning were as follows:

FC 2
CC 0
TA 80
ph 8.2
CYA 50
CH 470
Borates 50
Temperature 76

Per pool math it suggests adding 72 ounces of 20 Baum Muriatic acid to reduce my ph from 8.2 to a target of 7.5. It took 3 drops of Taylor reagent R-0015 (acid demand) to reduce ph from 8.2 to 7.5 suggesting that I need 30 ounces of 20 Baum Muriatic acid. That is a HUGE difference.
 
I am still very confused about the relationship between borate levels in the pool and acid demand. I know that the TF-100 test kit does not contain reagent R-0015 (acid demand) compared to the Taylor K-2006 test kit because Pool math can calculate the amount of acid needed to lower ph to the desired level. In my case Pool math simply does not work unless i put in a much lower value for Borates than my Lamotte test indicates. I know I added enough 20 mule team borax to raise my Borates level to 50 ppm last year. My pool uses about two pints of acid per week to maintain the proper ph. Does that sound right for an 11K gallon plaster pool with a TA of 80 and Borates of 50? For all of my other dosing calculations Pool math works perfectly. I wish I understood this and did not have to do the extra step of performing the acid demand test and buying the R-0015 reagent.
 
If you need to add acid regularly, you probably haven't balanced your levels correctly yet (or have high TA fill water, or extreme amounts of aeration).

Do you winterize? If so the borate level would be expected to go down significantly over the winter.

You don't need the "extra step", you already know that setting borates as 15 works.
 
I have a very similar issue, in that my pool demand acid daily. Everything is in balance, but with a SWG the pool can drift from 7.5 to 7.8 almost in a day. That's about 30-40z every two days. I do have a spa which aerates the water in the spillover.

The addition of the borates changes the calculation of acid to adjust pH - for my pool, it's nearly triple. While I don't have an acid demand test, poolmath has been spot on. I am not a chemistry master, but my recommendation is a) rely on poolmath and b) until you're confident in it, aim short with acid (especially if poolmath calls for a lot at one time).

I am debating about adding an acid doser in the future, but for now it's daily check and add.
 
I live in the north bay of the San Francisco bay area so I don't winterize my pool due to the mild climate. I don't have any water features or children that do a lot of splashing in the pool that would expose it to high amounts of aeration. Mostly my wife and I take dips in the pool in the summer to cool off. My water is clean and clear and I have never had an algae outbreak thanks to employing the methods taught by Trouble Free Pool. My total alkalinity is fairly stable and drifts down very slowly requiring me to add baking soda to the pool to raise it about once every two months. I add baking soda when TA goes below 70 ppm as suggested for plaster pools that do not have a SWG. Jason your suggestion of using pool math for the acid demand calculation by entering a much lower value for borates than I believe to be the correct value according to my testing would work but makes me feel a bit insecure and puzzled why my acid demand does not behave as I would expect based on all the reading I have done here. Except for understanding acid demand and borates I am completely confident in my execution of TFP pool care and testing methods.

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Let your TA go down to 60, or even 50, and see if that improves the PH drift issue.

Unfortunately, the borate test is not at all precise. While the acid demand behavior you have seen is far from a perfect borate test, it is probably more reliable than the borate test strips.
 
Now I am wondering if I should add more borates to my pool until my actual acid demand agrees with Pool math with 50 ppm borates and 80 ppm TA as the inputs and just ignore the Lamotte test.

Another question completely off topic is how do you add a picture to a post? I followed the directions in uploading a photo tutorial and I could not make it work. Has the procedure changed since the web site had been updated?

Thank you for all your help.
 

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I am already a Platinum supporter. That is the tutorial I tried to follow. It posted a link to photo bucket instead of the actual image. I have an apple computer. Would the steps be the same for my computer? Would TFP give me a message notifying me if I have used up my allotment?
 
I finally figure out how to upload photos. The tutorial did not mention that you have to click on the insert image icon on the TFP pool site and then click on "From URL" and paste the link form photobucket there. I still can't make it work in flickr but it seems to be working fine with photobucket
 
I just spent the evening reading past discussions on the topic of the effect of borates on acid consumption and realize this topic belongs in chemistry 201. I see that this topic has been discussed extensively in the past and the idea of relying on pool math as a substitute for the Taylor acid demand test has been controversial. I love pool math and think it is an amazing and brilliant tool and understandably TFP is invested in defending its accuracy. As much as I hate to suggest this it seems to me based on my own experience with the effect of borates on acid demand and what I have read in past discussions on this web site that it would be a good idea to recommend to those who use borates to do the Taylor acid demand test. I hope I don't offend anyone by putting that idea out there but it might help TFP members in reducing errors in acid dosing and maintaining proper ph.
 
PoolMath is hardly perfect, but it is more accurate than what your experience with it suggests. The apparent error you are seeing is so large that it can not possible be entirely because PoolMath is wrong, it must be at least partially because you are giving it incorrect information. There isn't enough information here to be sure of any particular level, but your borate level can't possibly be as high as 50. We have extensive experience with PoolMath and it has been spot on for thousands of people with and without borates. It does lose precision for large PH changes, but not to the point where it could be wrong to the extent your results suggest. That means something else must be going on, and the only obvious possibility here is that your borate level is much lower than you think it is.
 
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