MURIATIC ACID AND BORAX

[tvretired]

I am ready to close my pool and wanted to adust my chemistry before the closing. I pumped out enough water to drain my lines and have 47,000 gal left in the pool. My TA has been high all year and I want to get it down now to about 100-120. Current readings are: FC 7.5, CC.5, Ph 7.2, TA 140 down from high of 270, CH 370, CYA 50, Temp 52.

I have been using muriatic acid to lower the TA, which brings my Ph down. I tried aeration by hooking up my 3hp compressor to a piece of pvc with lot of little holes drlled in it and droped the pipe into the deep end and ran it for 1 1/2weeks. The Ph was very slow to react.

I want to add some borax to raise the ph, then use the acid to lower the TA. Since adding acid and borax rises the borate level, how do I avoid inadvertantly raising the borates too much? I ordered the boate test strips in July but they never came, so I called and they are resending them now.

Will use of acid and borax to adjust Ph and TA alwys result in raising borate level, or only if you add them both at the same time? How long should you wait after adding borax before adding acid to avoid borate increases?

 

[dmanb2b]

Will use of acid and borax to adjust Ph and TA alwys result in raising borate level, or only if you add them both at the same time? How long should you wait after adding borax before adding acid to avoid borate increases?

Unfortunately, this method will not be very effective in lowering TA. Muratic Acid lowers PH and TA and Borax raise PH and TA as well.

The only way to efficiently lower TA is via MA additions and areation to raise PH. TA of 130 is not that high, so it makes sense that the aeartion you applied was not as quick as you had expected...but 1.5 weeks of aeration does not sound right.

As far as your borate level...I wouldn't worry about it to much given you have a 47,000 gal pool...I'm guessing you would have to add 30-35 4.5lb boxes to raise your borate level to 50ppm.

 

[MikeInTN]

Anytime you add borax, you're raising the borate level in your pool. As dman pointed out though, it would take quite a bit of borax to get your levels up to anything real alarming. 12 oz of borax by weight raises the borate level 10 ppm in a 1000 gallons. So, to get 10 ppm in your pool (which is a low borate value, btw - most people here on the site who want borates in their water try to get 50 ppm), you'd need over 35 lbs of borax.

Borax doesn't raise TA as much as baking soda or washing soda, but it's not TA neutral; it will raise the TA when you add it. By how much, I don't really know. If adjusting TA was as easy as adding acid and borax until you got it where you wanted it, we'd all be doing it.

 

[polyvue]

I tried aeration by hooking up my 3hp compressor to a piece of pvc with lot of little holes drlled in it and droped the pipe into the deep end and ran it for 1 1/2weeks. The Ph was very slow to react.

This sounds like the aerating was taking place under water... I wonder if you'd have more success building an above water line device (many on this site have built an inexpensive apparatus from PVC pipe and connecting it to a return line.)

 

[duraleigh]

Throughout this swim season, I believe we have been guilty of "Muddying the water" on how to adjust pH and TA.

While not technically perfectly accurate, you can keep these straight in your mind if you remember that....


Muriatic.....lowers pH and TA roughly proportionately.

Borax......raises pH but has a much smaller affect on TA.

Baking soda......raises TA but has a much smaller effect on pH

Aeration/acid process.......Lowers TA without lowering pH.

Using those three chemicals and one "process", you can adjust either pH or TA (EDIT seperately to your hearts content.


So, do not use muriatic (EDIT by itself to lower TA.......in the long run it will not work without also lowering your pH. Instead, the primary action to keep in mind is to lower TA thru aeration.....(even tho it's not the aeration that does it) that will help you keep these adjustments clear in your mind.

(If the aeration was not working for you, perhaps your pH was not in the 7.0-7.2 range where aeration is most effective.)

 

[chem geek]

Any strong acid and strong base will move pH and TA together in the same amount -- that is, an amount of acid that is added will lower both and if you add enough base to get the pH back to where it was then the TA will get back to the same place as well.

Borax is a mostly strong base (at pool pH), but it also counts a little towards TA (because it's not really perfectly "strong"), but this is a small effect of only 5 ppm TA with 50 ppm Borates (again, at pool pH near 7.5). So using Borax to raise the pH will generally raise the TA almost exactly opposite as a strong acid.

It is pH Up (sodium carbonate) that raises the TA twice as much as a strong base (such as lye or approximately Borax). Essentially, sodium carbonate is identical to a combination of lye (sodium hydroxide) and baking soda (sodium bicarbonate).

 

[tvretired]

How this all started is my well water has a TA of 270 when I tested it straight out of the well. I had a heck of an algae problem last year and added a pile of dichlor to kil the algae on the recommendation of my pool co. This of course ran my CYA to 120, which brought me here at TFP to start with. I drained about 1/2 of my water and refilled with well water and repeated, driving my TA to 270 again but dropping the CYA to 40 finally. The pool co sold me acid to lower the TA and soda ash to raise the subsequent low Ph. I ran the TA up wih soda ash and then acid lowered the TA AND PH, so I had to add soda ash again, et, etc, etc. I even called the HTH toll fee number for advice, but they told me the soda ash - acid applications should not cause my TA and PH to move in such a locked togther fashion.

I read here that borax raises TA the least while raising Ph (compared to soda ash and washing soda), except for aeration. I read the articles on the chemical effects of aeration on "getting the fizz" out of the carbonic acid and thought aeration under water would be similar to blowing air thru a straw into a glass of pop. It would take all the fizz out. Am I wrong on that?

I will try aeration next spring because it is gettting just too cold to work on the darn pool anymore this year. I will order a fountain, such as the polaris ones, that use my Polaris booster pump to power the fountain. That should get me some aeration, especially if I add some return jet PVC aerators. I hesitated on this so far this year because it was just so darn cold already I ws afraid aeration would dump a lot of my water temperatue into the air and cool my pool even worse.

In short, it appears that using the borax - then acid cyce will still not reasonably get me to my goal of TA at 100-120 with Ph of 7.5-7.8. Correct?

 

[PaulR]

tvretired, that is one heck of a pool you got there.

I think you do understand the process, it's just that you have such a huge volume of water that aeration wasn't very effective. Sometimes I think "aeration" might not be the right word, the people with the "aeration" gizmos and the happy success stories seem to be agitating (churning) more than aerating (introducing air). After all, the point is to get CO2 out of the water, not O2 into the water. A fountain sounds like the right solution.

You should be fine where you are for the winter. The high TA in the fill water means you'll be going around again in the spring, but hopefully you will have more effective tools by then.
--paulr

 

[chem geek]

Well, introducing air into the water does in fact get the excess carbon dioxide out of it closer to the amount that is naturally in air. Yes, agitation of the water surface to break the surface tension and increase the area in contact with the air is helpful, but so is injecting tiny bubbles of air since air has a lower carbon dioxide concentration than pool water (pools are intentionally over-carbonated). Tiny bubbles are better because they have a higher surface area to volume ratio and the rate of diffusion of carbon dioxide from the water into the air bubbles is proportional to the surface area so for the same total volume of air, tiny bubbles have more total surface area. The analogy of blowing bubbles in soda pop to lower its carbonation is a good one.

Waterfalls, fountains, spillovers and even air compressors are are helpful, but as you point out with a large volume of water it can take quite a while for the pH to rise. What tvretired did with the air compressor and PVC pipe with small holes in the deep end of the pool was the right thing to do. tvretired, did you lower the pH significantly when you were doing the TA lowering procedure? The carbon dioxide concentration is increased in the pool at lower pH so that drives it out (into the bubbles and out of the pool) faster. Getting the pH to 7.0 is a critical part of the process and bringing it back down even if the pH only rose to 7.2 also makes things go faster.

Richard

 

[duraleigh]

TV,

I changed the focus of this thread somewhat (because of a pet peeve I have) and got it a little off track.....I'm sorry for the subject drifting.

I think MikenTN answered your first question about borates and I think Richard may have answered your question about the ineffectiveness of aeration without first reducing pH down to 7.0.

It's getting too cool even here in NC to mess with a pool too much so I understand your plan to wait for Spring. The aeration method you described will work if your pH is kept low enough for it to be effective.

 

[tvretired]

I am glad I checked back in with you folks. I had 8 boxes of borax ready to go in the pool yesterday, but now I think I will put them back in the case. My borate test strips should be here soon, so I will wait to find out what my borates are now before adding any more borax. I was impatient with the slowness of aeration and wanted to speed up the process of lowering the TA. Borax seemed the best, quickest method to use; certainly better than soda ash or washing soda. Aeration seemed too slow for my impatience to close the pool up before the ice formed on it!

tvretired, did you lower the pH significantly when you were doing the TA lowering procedure?

On Aug 26 I had Ph below 6.8 for a day due to acid addition, but I was not aerating at that time. When I ran that day's tests I immediately added borax because I was afraid the low Ph would eat at my heater's heat exchanger. I tried to keep my Ph between 7.2-7.8 during the process of drain and refill to lower the CYA because my kids complained about the water stinging their eyes when they swam. I had not yet started aeration since I was working only on lowering the CYA from 120. When I started to work on aeration I held my Ph in the 7.2-7.5 range so they could still swim. Next spring I will hold it at 7.0 and aerate while the water is still too cold to swim, before I open the pool on Memorial Day weekend.

I started fixing my CYA problem in mid-late July when I found TFP. By Aug 1 I had CYA down to 90 with Ph of 7.7 and TA at 270. By Aug 9, with CYA now down to 50, I had TA down to 170 & Ph 7.5 by adding acid to lower TA and borax to raise Ph. I had no borate test strips to test boates but I did get the TF Test kit by then. My Ph was in the 7.2-7.6 range consistently so we could use the pool in late Aug and early Sept since it had cleared up beautifully once the CYA was adjusted properly and the weather was unusually warm.

Interestingly, by Sept 22 my water temp had dropped to 74, so we quit swimming and I only added bleach to keep my FC up. From Sept 22 to Oct 4, with only my pump running, my Ph raised from 7.5 to 8.2. No aeration taking place during that time, other than the consatant rain we seemed to be getting. I added a toal of 2 1/2 gal acid from Oct 4-8 to lower TA from 160 to 140, stopping when my Ph dropped back to 7.2. That is where I sit today. FC 7.5, CC .5, Ph 7.2, CYA 40, TA 140, CH 270, Temp 51. Going to clean the last of the leaves out when it stops raining again (and again and again, etc all dang July,Aug and now Oct).

I just received what I need to drain the lines and add my RV antifreeze, so I wil leave TA for next spring. Once I do my start of season water addition to bring the water up to just below the top of the skimmer opening I expect my TA will be back to around 180 or higher again.

Thanks for all the advice. It is the only advice I've gotten that had proven to be both correct an effective!

 

[dmanb2b]

No aeration taking place during that time, other than the consatant rain we seemed to be getting.

TV...FYI, rain is a great aerator...as chemgeek mentioned..."agitation of the water surface to break the surface tension and increase the area in contact with the air is helpful, but so is injecting tiny bubbles of air since air has a lower carbon dioxide concentration "

 

[chem geek]

On Aug 26 I had Ph below 6.8 for a day due to acid addition, but I was not aerating at that time. When I ran that day's tests I immediately added borax because I was afraid the low Ph would eat at my heater's heat exchanger. I tried to keep my Ph between 7.2-7.8 during the process of drain and refill to lower the CYA because my kids complained about the water stinging their eyes when they swam. I had not yet started aeration since I was working only on lowering the CYA from 120. When I started to work on aeration I held my Ph in the 7.2-7.5 range so they could still swim. Next spring I will hold it at 7.0 and aerate while the water is still too cold to swim, before I open the pool on Memorial Day weekend.

I wouldn't worry at all about having the pH low at 6.8 or even lower for a short time such as days or even a week or two. The only reason we usually target 7.0 is that the lowest pH reading on most pH tests is 6.8 (on some it's 7.0) so by targeting the next-to-lowest reading you can be assured to not go too far. In practice, it takes far lower pH to start corroding metal that quickly or to dissolve plaster. Keeping the pH and saturation index reasonable are things to do over many months.

There have been quite a few pools that have used Trichlor and not adjusted pH and then reported that they have no TA reading which means their pH is below 4.5. Though I'm sure some of those pools had some sort of damage, not all seemed to and it was probably because these awful conditions didn't exist for too long. I'd never recommend going down to such low pH levels; my only point is that a pH in the 6.5 to 7.0 range isn't going to quickly cause damage. The pH scale is logarithmic so a change of 1.0 is a factor of 10 in concentration.

Richard