Help with TA and PH balance

[ducru]

I'm looking for help in balancing my TA & PH. It seems that no matter what I do, I can not lower my PH below 8.0-8.2.  I have tried with the TA between 70 and 90 PPM but the PH stays above 8.  I tried increasing the calcium hardness from 140, to 150 and now to 200, but the problem persists. I was using a '' PH-'' product (sodium bisulfate) and am now using the same product, but in liquid (citric acid, I believe), without success. Presently my TA level is at 90 , my calcium hardness at 200 and my PH is at 8.2. I have just added enough ''PH-'' to reduce the PH by .8 PPM, as per directions on the jug.  When I tested again just now, the PH is down around 8.0-8.1.  What is going on ?  How much of this stuff do I need to add before the PH starts going down ? Add to the issue, the fact that in the last 2 days, I must have added 12 TBSP of dry and another 10 of liquid PH- product into my spa.  How much of this stuff is safe to soak in ? I would like to protect my investment, but would also like to avoid melting away my limbs when I climb in !!  Any ideas ?  I know it's a popular topic, but I seem to be getting nowhere with what I've tried so far.  Thanks.

[Topline Mike]

You are very close.  My water is the same as yours.  If my TA is 80 or above, my pH will be 8.0 or greater.  I am sitting at 60 for a TA, and my pH is around 7.7.  I have been using muriatic acid to lower my TA.  Get your TA down to 50 or 60, and the pH will be 7.6 or 7.7.  Good luck. 

[ducru]

Thanks for the feedback Topline Mike. But doesn't the higher TA usually stabilize the PH ?  Will it not get worse if I lower the TA ?  Should I continue adding the PH- in the meantime ?

[Quickbeam]

Thanks for the feedback Topline Mike. But doesn't the higher TA usually stabilize the PH ?  Will it not get worse if I lower the TA ?  Should I continue adding the PH- in the meantime ?

Ducru,

It's the other way around. A lower TA will stabilize the PH, as long as you don't go too low. You need to add your PH minus and then run all your jets with the air injectors on. This is to aerate the tub. Once you've done this take both your TA and PH readings. Aerating the tub will normally cause your PH to jump up. When you reach the point that your PH no longer jumps up when you have aerated the tub, that's where you want you TA to be.

As an example, with my water conditions, I need to have my TA at 30 in order to prevent my PH from spiking up every time I run the jets. I would prefer it if I could have my TA a little higher, but with anything higher than 30 my PH jumps up when I run my jets. Remember as well that when you are aerating, run everything you can to get as much aeration as possible. When I do my water I run all the jets, with the air injectors on, and also run the waterfall.

Hope this helps.

[Quickbeam]

Ducru,

Check your e-mails. I sent you a PM.

[chem geek]

What the pool and spa industry often neglects to tell people is that TA is a SOURCE or rising pH and that TA is not just a pH buffer to stabilize the pH.  TA is a measure of the OVER-CARBONATION of the water.  Because of this over-carbonation, carbon dioxide outgases from the spa and that causes the pH to rise (with no change in TA).  This chart shows how over-carbonated a spa is compared to the equilibrium amount when in contact with air.  A higher TA or a lower pH will outgas faster so will have the pH rise and require more acid to compensate.

When people use net acidic sources of disinfectants or oxidizers, then a higher TA is appropriate to balance this net acidity.  So when using Dichlor or non-chlorine shock (MPS), then higher TA levels are OK up to a point.  But when using a hypochlorite source of chlorine such as bleach, one needs the TA to be lower.  One can add 50 ppm Borates (usually by adding boric acid) for additional pH buffering that doesn't have the side effect of carbon dioxide outgassing.

[ducru]

Hello all.  Thanks for all the feedback.  Thank you Quickbeam for the link.  This evening I used some ''TA -'', ran the jets with aerators on, and my TA fell to 60, while my PH was at 8.0-8.1.  I then added about 3 oz of liquid ''PH -'' (citric acid) and ran the jets and aerators again, for another 20 minutes.  This did not affect my TA, and did little to my PH, as it now sits at 7.9-8.0.   

chem geek, I have trouble understanding the OVER-CARBONATION  of the water and the outgassing of the spa issue. What you are saying is the higher I keep the TA or the lower I keep the PH, the PH will always be ''pulled'' towards A higher level ? But what creates this outgassing, how can I minimize it or do I even want to minimize it ? Does it have to do with the jets, with the aerators, keeping the spa (un)covered ?   

FYI, my hot tub is 350 gallons and I use lithium as sanitizer, in case this makes any kind of difference. Any ideas where I should  go from here ?

[chem geek]

You minimize the outgassing by not having the TA so high and by not trying to keep the pH too low.  Also keeping aeration to a minimum will reduce the rate of pH rise.  So if you run aeration jets, that will have the pH rise more quickly.

If you are using lithium hypochlorite as a sanitizer, then first and foremost if you have not used Dichlor at all even when starting up with the latest refill, then you should do that -- use Dichlor for cumulatively around 33-44 ppm FC.  That will build up 30-40 ppm CYA and then you can switch to using lithium hypochlorite.  Without any CYA in the water, the chlorine is too strong.  It will get used up too quickly and will oxidize swimsuits, skin, and hair too quickly, and degrade the hot tub cover faster.  At the other extreme, if you were to use only Dichlor, then the CYA would build up too much and the chlorine would become less effective usually requiring you to change the water sooner than you'd otherwise need to if you didn't use only Dichlor.  Note also that instead of using very expensive lithium hypochlorite you could use regular unscented bleach, if you wanted to.  Up to you since bleach can spill more easily than powders like lithium hypochlorite.

When using a hypochlorite source of chlorine like lithium hypochlorite or bleach (sodium hypochlorite), you'll want your TA to be lower -- probably around 50 ppm.  And if you lower the TA that much, then you'll want to add 50 ppm Borates from boric acid you can get at Duda Diesel or The Chemistry Store.

[ducru]

Hi Chem geek. I think I finally understand what's happening. Thanks for the explanation.
 With regards to dichlor, are you saying that I should shock my spa with dichlor to raise my FC level to 33-44 PPM ? Can I do that now, or only when I refill the tub ? In other words, is it OK to mix the two ?(lithium and dichlor) ?  Also, when I test for the CYA and it shows that I have attained my goal, do I simply go back to using my regular lithium ? Will the CYA remain stable at 40 PPM or will I have to repeat the process on an ongoing basis ? Should I use the dichlor to raise the CYA and also add the 50 PPM of borates ? There is a local hot tub store that sells boric acid specially packaged for the spa, but I don't really know how to test for the levels, once it's in the water. How do you know that you've attained the right level ? Thanks again for the assistance.

[chem geek]

No, don't shock your spa that high.  I was suggesting switching to using Dichlor after each soak (and in between soaks if there's a gap and you need to maintain the chlorine level) until you cumulatively add 33-44 ppm FC worth.  Or you can buy pure Cyanuric Acid granular (CYA) and add 30-40 ppm worth of that instead.  CYA takes a while to dissolve though in a hot spa it won't take as long as with a pool (in a pool one usually puts it in a sock and hangs it over a return or puts it in the skimmer so that there is plenty of water flow and even then it takes many hours to dissolve.

[ducru]

So, in other words, by adding the cumulative amount of 33-44 PPM of FC over a period of a week or so,  through the use of dichlor, I will create the required 30-40 ppm of CYA ? What about the boric acid; should I also add the value of 50 PPM ?

[chem geek]

Yes you understand that correctly.  Dichlor adds both chlorine (FC) and cyanuric acid (CYA).  The chlorine gets used up so adding more Dichlor maintains that level, but the CYA builds up so you want to stop the Dichlor and go with hypochlorite once you reach your CYA target.  Then, roughly once a month, you want to use Dichlor for a day to add some CYA that will be slowly oxidized by chlorine over the month (roughly 5 ppm).

As for the 50 ppm Borates, you'll add after your TA is down to around 50 ppm.  If you use Dichlor, it's net acidic so will lower your TA over time.  For every 10 ppm FC you add from Dichlor, it will lower the TA by 3.5 ppm.  So after adding 33-44 ppm FC of Dichlor, your TA should have dropped by 11.6 to 15.5 ppm.  If you need to lower it more, you do so by adding acid to lower the pH to around 7.0 or 7.2 and aerate the water -- every time you add acid it will lower both the pH and the TA while the aeration will only increase the pH with no change in TA.  After your TA reaches 50 ppm, you continue to aerate to get your pH to around 7.5 or so, then add the boric acid.  This should have your pH be much more stable from that point onward and you can use your lithium hypochlorite or bleach and not have the pH rise so much over time.

[ducru]

Thanks.  I'm on it !