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Hi Everyone,

I am new to the forums as a poster but have been carousing them here, at TFP, and at TPF for many years. I work for one of the largest pool builders in North Texas, managing the supply store. Before you crucify me, our margins are very low (we do high volume) and we are honest with people about pool care.

Anywho, I am looking for answers as to the effect of Borate on the SI calculation. I can not seem to find any straight answers on the internet.

We have found through our experience that with a borate at 80 (we tell people about the NOAEL levels and to stop their pets from drinking out of the pool) and the TA reading at 60 PPM the PH will not fluctuate despite fill water/rain water/trichlor.

This is my pool chem:

FC - .8 
TC - .8
CC - 0  

PH - 7.4 

TA - 60 

CH - 225 

CYA - 20 PPM

Borate - 40 - 80 

I use PoolRX for algae control + assist in sanitation and CV-700 for bio-oxidation/phosphate control. 

I understand that Borate and CYA have an effect on total carbonates, but I am at a loss to find what the Borate calculation is. 

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The Borates only modestly affect the SI calculation.  You basically subtract their contribution to TA, just as you subtract CYA's contribution to TA.  You can use Pool Math and it will calculate the CSI for you automatically accounting for the CYA and Borates levels you enter.  50 ppm Borates lower the CSI by about 0.05 units at a pH of 7.5 or by about 0.1 units at a pH of 8.0.

Note that the maximum Borates (ppm Boron) level allowed by the EPA is 50 ppm so you won't see any product labeling going higher than that.  If you've been following TFP, then you should know that you don't need copper ions (PoolRx) for algae control if you maintain the proper FC/CYA ratio.  Your CYA level is quite low for maintaining chlorine in sunny areas.

Hi Richard,

Thanks for the straight answer. I am also curious as to the effect Borate has on water with a lower SI. Would it buffer against the solubility of the calcium compounds in plaster?

I understand the BBB method, but in my area I have a lot of people that are concerned with DBP and general exposure to chlorine, especially when the EPA talks about not entering a pool that has chlorine higher than 4 PPM. So when I explain the CYA/FC ratio and how it is supposed to work and they hear 5 PPM FC with a CYA of 50 PPM they don't want to do it. Yuppies. 

So about three years ago I started experimenting with different ways to maintain a chlorine residual of around 1 PPM without having issues with sanitation, cloudy water, and algae. 

I found that by combining Borate, Mineral Feeder (PoolRX and Nature 2 both work), and Enzymes (at period just before the most use weekly) - maintaining a residual level of chlorine between .5 - 1.0 PPM keeps the pool nice and clear no matter the bather and organic load. I have a 15,000 gallon pool and I maintain that level of chlorine with only 1 tablet per week and I keep the CYA at about 15 - 20. 

Since Enzymes degrade oils and non-living organic matter, organic reactions with chlorine are minimized, thus minimizing DBP (which from what we have tested in regular chlorine pools is usually only a large issue after heavy bather loads with oil/lotions getting into the pool - but in pools when enzymes are added just hours prior to heavy bather load the THM content is lower)

I would say that maybe it's just my pool somehow defying chemistry, but I have hundreds of pool owners having done it this way for the better part of three years and we are seeing no health issues, algae issues, cloudy issues etc. I also have not super-chlorinated in over a year. We also are not seeing any issues with staining/plating from the use of PoolRX - they say they have a bonded chelator, plus I suspect with backwashing, mineral depletion, lack of super-chlorination and the added buffer of borate the minerals hold into solution.

The BBB is great, especially for pool owners willing to monitor their pool like they should. Unfortunately in my area we have a lot of reactive, not proactive, pool owners.

So if you want to run a pool at a lower FC/CYA ratio, you can do that by using a phosphate remover.  The copper ions work as well but can stain plaster so I wouldn't use that except for vinyl pools though if you get phosphates down towards 100 ppb then algae growth will be so slow that small amounts of active chlorine will kill it.  That will let you have 2 ppm FC in the pool but with 60-80 ppm CYA instead of the 20 you have now.  That will use less chlorine lost to sunlight.  If you can maintain 1 ppm FC, then 30-40 ppm CYA would be OK.  Again, only if you are preventing algae growth with supplemental methods such as phosphate removers.

There are so little DBPs in low bather-load residential pools that it should not be an issue.  In my own pool I never measure anything significant -- it's always <= 0.2 ppm and technically likely <= 0.1 ppm CC and that's mostly chlorourea which is a non-issue anyway.  Your Trichlor tabs are producing way more noxious nitrogen trichloride just dissolving in the water concentrated in their feeder compared to using a hypochlorite source of chlorine and is why you smell chlorine near such feeders.

You could try not using the enzymes on some pools and see if you notice any difference.  Also, if you truly keep phosphates low, then the PoolRx shouldn't be necessary.  It's an either/or sort of thing though I suppose having two is like insurance in case the level of one drops (i.e. phosphates get too high or copper ion concentration gets too low).

Thank you, Richard. I have learned an untold amount of information from reading your posts here and on TFP, and your posts on Borate safety has really helped me help a lot of pool owners understand the benefits of Borate.

Many thanks for your expertise and very scientific explanations throughout the internet!


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