Boric acid trouble.

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D

DrK

0
Jun 8, 2014
7
Albuquerque, NM
My CYA was too high and so I emptied about 2/3 of my pool, readjusted everything so that pH 7.4, FC 9.0, TA 160, CH 250, CYA 70 with crystal clear water. I then added 99% boric acid at the amount noted in the pool calculator. I added it a couple of pounds at a time which I pre mixed in a 5 gal bucket. It was recommended that I use boric acid rather than borax with a high CH to avoid precipitating calcium. I had previously used borax in my hot tub with no problem. About an hour after adding the boric acid, my pool remains cloudy. pH after boric acid is 7.4. Is there any chance that this will clear or do I have to empty my pool.

Thanks,
KE
 
Yes, my intention was to add borates to my pool. I pre mixed a few pounds at a time in a 5 gallon bucket which gave me a white slurry that I added slowly to the pool. I didn't see any specific articles on adding boric acid as there was on Borax + muriatic acid which I had done successfully previously. I read several posts which did not seem to indicate any special guidelines for BA.
Thanks, KE
 
Welcome to TFP! :wave:

You normally would lower your TA level before adding them and it's an optional and advanced procedure (not something you do until everything else is in shape). Your TA level is high at 160 so would normally tend to make the pH rise. What source of chlorine are you using (e.g. chlorinating liquid, bleach, Trichlor tabs, Cal-Hypo, etc.)? Also, what test kit are you using? As for adding borates, if you use the granular form of boric acid we recommend, then that is just added slowly over a return flow and then any excess brushed to dissolve. Did you use powdered boric acid instead? The cloudiness will likely dissipate from any clumpiness dissolving or getting caught in the filter.

(Note to Dave: We should modify the So you want to add borates to your pool--Why and how with some info on using boric acid granular and how to add it.)

High concentrations of borates inhibit algae which is a plant. As noted in this link, "Boron is an essential micronutrient for higher plants, with interspecies differences in the levels required for optimum growth." Tests to determine the optimum level of boron in the soil showed that "approximately 82% of the plants exhibited the best growth at concentrations from trace to 5 mg/litre" and that "that there was overlap of the beneficial and injurious effects of boron between species". Basically, if you dump pool water with 50 ppm borates for watering plants, you should dilute the water by doing regular watering as well.
 
Thanks for the response. I use 8.25%liquid bleach and have a Taylor 2006 kit. I used boric acid powder and so that may be part of the problem although I read numerous posts from people who had used it without issues. I did premix it and so did not see clumping but it appears as if it is in suspension and after 4 hours, I don't see any sign that it is clearing. I have a water current generator that makes the pool like a rushing river. I ran this for several hours and so I am certain that the pool is very well mixed.

I am concerned about dumping water with 50 ppm borates on my grass. It's true that borate is an essential micro nutrient but it it also an herbicide at higher concentrations as it drys the plant out and inhibits photosynthesis. I don't know where the cutoff is. If I need to dilute by a factor of 10, I need to irrigate 10,000 gal for every 1,000 gal drained on the lawn. This may be a consideration for people who may at times need to empty all or part of their pool. They should perhaps think twice about borates if they don't have a place other than their lawn to empty the water.
Again, thanks for your help. In the past, I used the recommendations for borax with muriatic acid with no problem and so was confused with today's results.
 
Some people used powder OK and others had problems. It shouldn't be in suspension and should dissolve so perhaps it just acted as nucleating sites for calcium carbonate since your pool is roughly saturated. If you lower the pH and it clears up then that's what happened.

Yes you are right that those using borates should be careful about dumping water into areas with plants. It probably needs around 5:1 dilution for most plants but some may not tolerate even that much.
 
When you say "plants" does that include grass ??
This is my first year with borates and I backwash into my lawn which then runs down a slope into a couple acres of uncut prairie. So far the area of lawn doesn't show any adverse signs but now you have me looking.
We have been having an unusually high amount of rain and I'm wondering if in a normal year I'd need to, or it's advisable to "rinse" the area after backwashing ??
 
Yes, plants includes grass. In the link that I gave alfalfa was somewhat more tolerant of boron, but 50 ppm is still above normal tolerance levels. If you have rain, that will certainly dilute the borates especially if you have a slope with runoff (so it won't tend to build up in the soil). I can't say whether a normal year for rain would be enough, but it likely would since usual rain is a lot of water compared to the amount you backwash, depending on the size of the area that retains the water. 1" of rain over a 100 square foot area is 62 gallons. That's about a minute of backwash at 60 GPM.

You can just see how your plants do. The main symptom of too much boron is yellowing tips of leaves or blades.
 

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I’ve tried to answer my question. This article is the most extensive review on borates and plants that I can find: http://www.jipb.net/tupian/2008/6/10/101718.pdf
As far as I can tell, grass is fairly boron tolerant but some plants, like pines, are very sensitive to boron. Water plants are also very sensitive to boron – hence its algaecidal properties. Some areas have high boron levels in the soil; arid areas like the desert southwest and especially the California desert. Since borates never break down, draining your pool on your lawn would only augment an already high level. This reference lists sensitivity of some plants to boron http://www.fao.org/docrep/003/T0234E/T0234E05.htm#ch4.1.3
 
Thanks for the additional links. Note that even the "tolerant" level is 4-6 mg/L and the very tolerant level is 6-15 mg/L, both of which are far lower than the 50 mg/L in your pool water. You basically can't use your pool water as the sole water source, but it sounds like you aren't doing that anyway.
 
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