Strange issue adding tetra borate product

[Pauly B]

Hi all. I have had my pool resurfaced and decided to be my "pool guy" which I am doing an decent job at. Learned tons and did plenty of research and all the major concepts make sense. Been using a Taylor K-2005 doing many tests to get my testing skills up.

I decided to add a popular tetra borate product bought from an online retailer. 55# was initial recommended dosage for my 18,500 gallon pool. Per pool contractor and product customer service rep recommendations I waited until pool curing was done. Until this point I had been adding lots of acid to keep rising pH down. From what I've been told new plaster will cause this. I was looking forward to the buffering offered by the borates. and hoping to see pH settle in.

My TA was just around 80 when I added the product in two parts 8 hours apart. I was expecting the advertised "slight increase" in TA but what I got was a 140ppm increase!!!! Now I'm sitting at 220. A few rounds of acid has got it down to 200 and pH around 7.6. My SI is right at 0.5 so not panicking just yet. I decided to make a few calls. Started with Taylor to see if there was a known false testing issue with what I added and then to product manufacturer for their take.

Taylor said basically the only way to increase TA 140ppm was with sodium bicarbonate. Not his opinion or company line but "laws of chemistry". Product manufacturer was a little shocked to hear this and said give it 2 weeks and recheck. I am currently away from pool and without borate test kit but will check the level when I get home.

My initial thought is this. Did I get sold a bunch of baking soda in a borate bucket????? If I get home and test water and see no borates and my TA is still 200 what other explanation is there?

Thanks for reading

Thoughts?

PS not naming names until I get to the bottom of this to be fair

 

[JamesW]

Assuming that you added 55 lbs of sodium tetraborate pentahydrate to 18,500 gallons of pool water, that would increase the TA by 121 ppm and the borate by 53 ppm.

When adding sodium tetraborate pentahydrate, you have to add acid to offset the rise in TA.

For 55 lbs of sodium tetraborate pentahydrate, you would need to add 4.3 gallons of acid to offset the rise in TA.

The instructions for the product should say that you need to add acid when adding the product.

What exact product did you use?

You can check the numbers for yourself with PoolMath.

PoolMath

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You can calculate the effects of adding chemicals in the section called Effects of adding chemicals near the bottom of the page.

You can also calculate the amount of product needed for a particular result.

For a TA neutral result, the correct product to use is boric acid.

Note: There are several chemicals that can raise TA. Sodium tetraborate pentahydrate, sodium tetraborate decahydrate, sodium hydroxide, sodium carbonate and sodium bicarbonate will all raise TA.

 

[Pauly B]

To follow up on this I used SupremePlus and the high Total Alkalinity was a false reading. It did indeed settle down after 2 weeks. My local TexSun store swore this was the case and they were right.

 

[JamesW]

The product looks to be comprised of about 40 to 50% boron trioxide and about 40 to 50% baking soda.

The boron trioxide should be roughly pH and TA neutral.

B₂O₃ + 3H₂O --> 2H₃BO₃

Assuming 40% bicarb, the TA would increase by about 85 ppm.

To get back to the starting TA, it would take 3 gallons of 31.45% muriatic acid.

What do you mean that the TA reading was a false reading? If that's what it tested at, that's probably what it was.

What do you mean it settled down? How much acid did you have to add to get it back down to what number?

 

[Pauly B]

What do you mean that the TA reading was a false reading? If that's what it tested at, that's probably what it was.

What do you mean it settled down? How much acid did you have to add to get it back down to what number?

Before adding SupremePlus it was 80. Then it tested at 220. Got it down to 180 then did nothing when pool store guy swore it was a false reading. It then just started testing at 90 and has been there since. I had been taking notes about SupremePlus weeks before I added it and while I can't remember the source there were two references to a false high TA.

Not sure what really happened but all is well and CSI is 0.02 so I have no complaints

 

[JamesW]

Ok, seems odd. I don't know what a "false" high TA is or why it would suddenly just disappear.

As best as I can tell, the "secret ingredient" is baking soda, but I don't know why it would be in the product.

The boron trioxide basically hydrates to boric acid. So, it seems to me that the product should just be boric acid.

In any case, I'm glad that you got it to where you're happy with everything.

In the future, I recommend that you just use boric acid if you want to add borates.