The Great Tetraborate Experiment!

[waterbear]

I calculate that 6 oz. of Muriatic Acid in 6850 gallons with your other numbers would lower the pH from 7.7 to 7.60 (or 7.6 to 7.49) due to the 50 ppm of Borates that help buffer the pH. With no Borates, you would go from 7.7 to 7.47 or from 7.6 to 7.40 so I'm not sure what's going on with what you saw. It could be in the ballpark for the 0.1 drop, but it seemed like you saw something closer to 0.2

Richard

Richard,
Like I said the pH was 7.6-7.7 as best as I could tell before I added the acid. After it was sitting right at 7.5 so I guess it was closer to 7.6 than 7.7 -- a .1 change in pH is probably about right.

It is definitely in the ball park!
So, my question to you is....When are YOU putting borates in YOUR pool?

[chem geek]

So, my question to you is....When are YOU putting borates in YOUR pool?

Since the pool is used by both my wife and I and she uses it during the week when I don't, she has the final say in this. I've talked to her about adding salt (to around 1000 ppm) for a silkier feel and about adding Borates as well and she's game. So now the ball is in my court so I just need to get my lazy butt off the couch and do it!

[chem geek]

I sent an E-mail to Taylor Technologies about creating a drop-based test kit for borates (ppm Boron). They said that they have just introduced a kit for testing Boron, but it is designed for industrial water as one drop measures 0.2 or 0.5 ppm (similar to their FAS-DPD chlorine test). I don't see this on their website yet, but it could still be useful if one were to do a 10:1 dilution and use the 0.5 test (to get within 5 ppm). It sounds like the ProTeam strips (or the ones from LaMotte) are still the way to go since they are close enough for accuracy and very easy to use.

Richard

[waterbear]

It sounds like the ProTeam strips (or the ones from LaMotte) are still the way to go since they are close enough for accuracy and very easy to use.

Richard

I have been using the Aquacheck borate strips which I believe are identical to the Proteam strips. Have not been able to find the LaMotte strips for sale anywhere either locally or on the net. I have ordered the Aquacheck strips from here
http://www.diywatertesting.com/
Cheapest price I could find, free shipping, and I got my oder in 3 days!

[chem geek]

waterbear (Evan),

I ran through some numbers on my spreadsheet assuming certain levels in your salt pool with borates and low TA. If I put in a pH of 7.5, TA of 70, CYA of 75 (for your SWG), CH of 300, TDS of 3200 (or salt of about 3000), 50 ppm Borates (Boron), and a temp of 85F, then this gives me a carbonate alkalinity of only 39 and a calcite saturation index of -0.47 (pool-store Langelier is -0.39). Now I know we don't give much credence to these indices and problems aren't normally seen until around +/-0.7 or even +/-1.0, but even so, the exceptionally low carbonate alkalinity in your pool plus the high salt level make the water more corrosive.

I just wanted you to know this and to be on the lookout for any signs of such corrosion, namely any dissolving or pitting of plaster/gunite/grout. If you notice your calcium hardness increasing (or not decreasing as much as it normally does, if it decreases from backwashing), then that would be a sure sign of trouble.

Assuming your CYA is high for the SWG (at 75 ppm), then a TA of 100 (carbonate alkalinity 69 and relative outgas rate 6.0) shouldn't outgas that much carbon dioxide, though it would be at about double the rate of a TA of 70 (carbonate alkalinity 39 and relative outgas rate 2.9). A TA of 100 would bring the "index" to -0.22 while also increasing the CH to 500 would bring the index to -0.01.

Richard

[waterbear]

Richard,
I run a adjusted TA of about 70 ppm (which means I run a TA of about 90), pH of 7.6, salt about 3400 ppm, Cal around 220-250 ppm, and temp around 82 when the heater is on. See what those give. BTW, I have seen no corrosive action to the water. Try plugging those numbers in and see what you get.
Evan

[chem geek]

With the higher pH and TA, this increases the saturation index. The higher salt level and lower CH (235) decrease it somewhat. The net result I now get is -0.35 which is better than the -0.47 I was seeing before. The actual carbonate alkalinity is 57.0. If I remove the Borates and keep the measured TA the same, then I get a carbonate alkalinity of 64.4 so though the Borates do not have a large effect, they do have some effect on alkalinity and therefore any "adjustment" calculation.

I'm glad to hear that you resolved your rising pH issue by lowering the TA only to 90 instead of 70, especially with the high CYA levels needed for the SWG. That makes this "lower TA" recommendation more reasonable for people combating rising pH without having to adjust too much of the other parameters.

If you increased your CH to 300, the saturation index would be -0.21; increasing it to 400 would make the index -0.09. Of course, raising the pH by 0.1 raises the saturation index by the same amount and is another alternative. Since you're not seeing any problems, you could of course just keep things as they are. Raising the CH to 300 or 400 wouldn't be hard now that you've stabilized your pool with all its parameters tweaked the way you want them (i.e. borates, salt, CYA). Just FYI.

Richard

[Ciscokid]

Hi ,
Today I started my quest to get my borates up to 50 ppm. I went to home depot to get some muriatic acid. The first thing I noticed is that it looks like water. I haven't purchased acid since last season. The acid I had from before was yellow in color. I looked at the ingredients and it has 14.5% acid. Unfortunatly I didn't have any left over acid jugs from last season to see if they lowered the percentage of acid. I know the acid I had before would almost knock you out if you caught a smell of it. This stuff doesn't do a thing. Has anyone else noticed any difference? I am in California Modesto area.
Chem Geek when you calcualted the amount of acid per box of borax what percentage was it for? Maybe this is the reason why I am having to add so much acid to my pool to get a change. If in fact the percentage has changed. Well off to add some borax and acid to the pool. cya

[waterbear]

They are selling acid that is weaker in strength now. Don't know if it's a safety issue or what but regular pool acid would be 20 Baume or 31% by weight. This stuff they are selling is about 10 Baume so it is half strenth. I've noticed the price is the same!

The borax calculations for acid are for 20 Baume or 31% Muriatic acid!

[chem geek]

Yes, my calculations (in the spreadsheet) are for Muriatic Acid that is 31.45% Hydrochloric Acid that has been a standard for a very long time.