Lowering Total Alkalinity - Hot Tub Water Chemistry - Pool and Spa Forum

Jump to content


(July 17, 2014) POOLSPAFORUM.COM SITE UPGRADE!


Photo

Lowering Total Alkalinity


  • Please log in to reply
69 replies to this topic

#1 Nitro

Nitro

    Spa Guru

  • Members
  • PipPipPipPipPip
  • 779 posts

Posted 03 April 2009 - 10:05 AM

This topic comes up quite a bit. I explain the process in my Maintenance Guide, but I thought I'd post a separate thread for easy reference. I won't get into detail why you would want to do this here. See my guide for more info. I will say this, the key is, you should NOT focus on adjusting pH directly. Instead, you should focus on adjusting TA to an ideal level, in order to keep your pH in line.

The problem with lowering Total Alkalinity (TA) is that when you add acid to lower TA, pH also decreases. This limits the amount you can lower TA without pH becoming too low. However, there is something you can do to raise pH that leaves TA alone, Aeration. Aeration is the process of turning on all the jets and air features in your tub, in order to pump as much air into the water as possible. By adding Acid and Aerating you can lower TA, while keeping pH the same.

One thing to remember is, the amount that TA decreases is directly proportional to the amount of acid you add. That is, in a 350 gal tub, 8 oz of Dry Acid will lower TA by 100ppm. It is important to know (by calculating) how much Total Acid you need to add to your tub in order to get to your Target TA.

The other thing to remember is, the higher your TA, the less effect acid will have on your pH. If your TA is high, adding acid won't effect it much. This confuses some beginners (and experts alike), which causes them to give up on lowering their pH. Because of this, you need to add more Acid in the beginning, and less as you get closer to your Target TA.

So, let's get started. Here is the process.

1. Turn on all your jets and air features and keep them on the entire process. (i.e. Aerate)
2. Calculate how much you want to lower your TA, and how much acid you need to add to lower it.
3. Add to the tub HALF (not > 1 cup nor < 1 TBS) of the amount of the remaining acid you need to add.
4. Aerate for 30min, and check TA/pH.
5. If TA > Target and pH is > 7.8, goto step 2.
6. If TA > Target and pH is < 7.6, goto step 4 one time.
7. If TA > Target and you can't get pH > 7.8 via aeration, Target too low. Stop here.
8. If TA = Target and pH is > 7.8, Target too high. Lower Target TA and goto step 2.

Example:
Your TA is 300ppm, you want to lower it to 60ppm, in a 350 gal tub.
To lower TA by 240 ppm you need to add a total of 2.4 cups (~19oz) dry acid.

Turn jets/air on.
Add 1 cup acid and Aerate 30mins.
Check TA/pH. TA=200 and pH>8.0
Add 6 oz acid and Aerate 30mins.
Check TA/pH. TA=125 and pH>8.0
Add 3 oz acid and Aerate 30mins.
Check TA/pH. TA=90 and pH>8.0
Add 2 oz acid and Aerate 30mins
Check TA/pH. TA=65 and pH=7.8
Add 1 TBS acid and Aerate 30mins
Check TA/pH. TA=60 and pH=7.6

The main thing to remember is, you add more acid in the beginning of the process, and taper off toward the end. This method will allow you to lower your TA in a matter of a few hours regardless of how high your TA is.

Lastly, safety is priority one. Be careful with any type of acid, especially Muriatic. If you're using Muriatic acid, wear rubber gloves and eye protection. Muriatic Acid is nasty stuff. Dilute all acid in a bucket of water and slowly pour mixure over a return flow, or middle of tub. Be careful not to splash. When mixing Acid and Water, always add Acid to water! NEVER ADD WATER TO ACID!!!

Happy Tubbing! smile.gif
Nitro's Approach To Water Maintenance
A guide to Water Balance and Sanitation using Chlorine

Lowering Total Alkalinity
How to lower TA, without lowering pH

Chlorine Demand (CD)
What is it, and why you should care

Decontamination
How to Super Shock your Tub

#2 chem geek

chem geek

    Wizard of Water

  • Members
  • PipPipPipPipPip
  • 4,800 posts
  • Gender:Male

Posted 03 April 2009 - 02:44 PM

Thanks for the great write-up. The relationship of pH and TA and how a high TA causes the pH to rise and how aeration plus acid addition are used in combination to lower the TA are all topics that confuse many and are counter-intuitive, yet the science behind how it all works is very clear.

#3 PA Mike

PA Mike

    Newbie

  • Members
  • Pip
  • 5 posts

Posted 12 August 2009 - 07:24 PM

This forum is great! I have a question. Is it ok/accurate to balance at a cold water temp, as in 54 degree well water?

#4 Nitro

Nitro

    Spa Guru

  • Members
  • PipPipPipPipPip
  • 779 posts

Posted 13 August 2009 - 02:55 PM

QUOTE (PA Mike @ Aug 12 2009, 10:24 PM) <{POST_SNAPBACK}>
This forum is great! I have a question. Is it ok/accurate to balance at a cold water temp, as in 54 degree well water?

Yes. You're probably going to need to fine tune over the course of a few days anyway. Just keep an eye on pH, and adjust TA accordingly.
Nitro's Approach To Water Maintenance
A guide to Water Balance and Sanitation using Chlorine

Lowering Total Alkalinity
How to lower TA, without lowering pH

Chlorine Demand (CD)
What is it, and why you should care

Decontamination
How to Super Shock your Tub

#5 PA Mike

PA Mike

    Newbie

  • Members
  • Pip
  • 5 posts

Posted 13 August 2009 - 06:35 PM

QUOTE (Nitro @ Aug 13 2009, 03:55 PM) <{POST_SNAPBACK}>
QUOTE (PA Mike @ Aug 12 2009, 10:24 PM) <{POST_SNAPBACK}>
This forum is great! I have a question. Is it ok/accurate to balance at a cold water temp, as in 54 degree well water?

Yes. You're probably going to need to fine tune over the course of a few days anyway. Just keep an eye on pH, and adjust TA accordingly.

Thanks. I've got the process started. I should be up to temp tomorrow, as I have the heater on now. I let it go a few days and picked up 15 degree temp rise for free. My TA/ PH balancing has never gone very well. I may have more questions after things get up to temp.


#6 sundance_majesta

sundance_majesta

    Newbie

  • Members
  • Pip
  • 3 posts

Posted 27 April 2010 - 08:53 AM

Hello,

I have been reading (and re-reading) this web site, and I'm switching over to the dichlor-then-bleach method after following the decontamination procedure.

My question is: My TA is 80, my PH is 8.0. So I need to lower my PH without lowering my TA right? (the opposite of this thread).

If I use muriatic acid, I will lower both, right?

#7 chem geek

chem geek

    Wizard of Water

  • Members
  • PipPipPipPipPip
  • 4,800 posts
  • Gender:Male

Posted 27 April 2010 - 01:35 PM

I would lower the TA until you get some pH stability. So if your TA is running high right now, then lower BOTH pH and TA by adding acid (such as Muriatic Acid, but be careful with that stuff -- you don't need very much and it's potent which is why dry acid is usually used in spas). Don't try and raise the TA after lowering the pH. Just see how your tub responds at a lower TA level. Odds are, after switching to bleach after a week or so of Dichlor that you will need a low TA of perhaps 50-60 ppm. If you still find the rate of pH rise too high, you can also use 50 ppm Borates.

#8 sundance_majesta

sundance_majesta

    Newbie

  • Members
  • Pip
  • 3 posts

Posted 28 April 2010 - 01:38 PM

Thank you for your help.

I added 1/3 oz of dry acid. 24 hours later, my TA stands at 100, my PH stands at 7.6. PERFECT!!

Joe

#9 sundance_majesta

sundance_majesta

    Newbie

  • Members
  • Pip
  • 3 posts

Posted 07 May 2010 - 01:56 PM

Thank you for your help so far.

Right now I'm getting PH: 7.4, TA: 40.

Do I need to worry about getting the alkalinity up?

#10 chem geek

chem geek

    Wizard of Water

  • Members
  • PipPipPipPipPip
  • 4,800 posts
  • Gender:Male

Posted 07 May 2010 - 05:26 PM

If your pH is stable and you are no longer needing to add any acid, then you can leave the TA where it is. Otherwise, if you're still adding some acid, you should probably keep the TA between 40-50 ppm so raise the TA to 50 ppm before you add any acid to lower the pH (in the future -- your pH doesn't need lowering now).

I presume that your TA dropped due to acid addition over time.

#11 footie

footie

    Hot Tub Aficionado

  • Members
  • PipPipPipPip
  • 376 posts

Posted 22 April 2011 - 09:45 AM

Bit of a dilemma, brother-in-law has added pH-UP to increase his pH but in doing so his TA has jumped to beyond 300. The problem we have is that pH is still low, like only 6.8-7.0.

What can I do?

#12 chem geek

chem geek

    Wizard of Water

  • Members
  • PipPipPipPipPip
  • 4,800 posts
  • Gender:Male

Posted 22 April 2011 - 07:02 PM

Run the jets to aerate the water and the pH should rise. When it does, add acid which will lower both pH and TA. Keep it at. It will take a while and a lot of acid, but the TA will go down with continued aeration with acid addition.

#13 footie

footie

    Hot Tub Aficionado

  • Members
  • PipPipPipPip
  • 376 posts

Posted 23 April 2011 - 06:55 AM

Feel a bit stupid here. Blame the effects of a bottle of nice wine because I misread the instructions on the TA test tablets container, I thought it said red to turn yellow instead of the other way round, so instead of having a high TA reading it was the opposite being very low. Amazing what a bit of sleep and a clear head does for you, anyway the fix was much quicker than the other way round and they are in the tub as I write.

#14 moscik81

moscik81

    Newbie

  • Members
  • Pip
  • 7 posts

Posted 13 June 2011 - 06:34 PM

any idea where i can buy dry acid in a local store ????

#15 Pools Plus Inc

Pools Plus Inc

    Newbie

  • Members
  • Pip
  • 6 posts
  • Gender:Male

Posted 03 February 2012 - 06:21 AM

any idea where i can buy dry acid in a local store ????



Most local pool or spa stores will carry pH Decreaser. They offer it in different sizes. Most spa sizes are one pound. You can also find the same great products online too.




#16 chem geek

chem geek

    Wizard of Water

  • Members
  • PipPipPipPipPip
  • 4,800 posts
  • Gender:Male

Posted 19 September 2012 - 05:04 PM

You can use The Pool Calculator to answer your question, but basically 25-1/2 fluid ounces of full-strength Muriatic Acid (31.45% Hydrochloric Acid or 20º Baume) in 10,000 gallons lowers the TA by 10 ppm. So this is about 1-1/2 fluid ounces per 100 gallons for a 10 ppm reduction in TA.

When you use Dichlor, which is what I presume was your "granulated chlorine", that is net acidic. This is because chlorine usage/consumption is acidic so continued use of Dichlor will lower your TA, just as if you are adding acid. Every 10 ppm FC you add from Dichlor lowers the TA by 3.5 ppm and increases the CYA by 9 ppm. If your pH rises just from carbon dioxide outgassing, then the TA will drop slowly over time. If you need to add acid, it will drop more quickly. If you add a base to raise the pH, then the TA will rise slowly over time (unlikely because you probably do have carbon dioxide outgassing which is quite common in spas, especially with aeration from jets).

#17 chem geek

chem geek

    Wizard of Water

  • Members
  • PipPipPipPipPip
  • 4,800 posts
  • Gender:Male

Posted 20 September 2012 - 06:01 PM

Well, the first step in lowering the TA is to get the pH down to around 7.0 and start aerating so you can certainly do that if you want. It won't drop the TA by too much and at least you'll get your pH down. 8.7 sounds high enough to cause problems with scaling, especially in the heater, unless your CH level is very low.

#18 waterbear

waterbear

    Village Idiot ;)

  • Moderators
  • PipPipPipPipPip
  • 3,279 posts
  • Gender:Male

Posted 28 September 2012 - 02:32 PM

As a general rule titrations are done until one additional drop produces no further color change and the you don't count the drop that caused no further color change. There are a few exceptions such as the salt titration test and borate titration (which is NOT offered by Taylor), where you stop at the first color change to the desired color and do not go past.
So for your TA test if it takes 9 drops to change to a red, the 10th drop produces a brighter red,and the 11th drop does not change the color any further your result is 10 drops.

http://www.taylortec...e_slideshow.asp
Click on pool/spa in the upper left and then scroll down and see videos of how to do the different tests in the K-2006 (and some of their other kits) and also some general testing info videos.
You can view the CYA test and see what it is supposed to look like.
Finally here is some additional info on lowering TA that you might find useful. It also discusses the relationship between TA and pH.
http://www.poolspafo...showtopic=36290
Follow the link in the above post (to the swimming pool water chemistry section of the forum) and read.
I've tested more water than I ever care to think about!
Board Moderator

#19 chem geek

chem geek

    Wizard of Water

  • Members
  • PipPipPipPipPip
  • 4,800 posts
  • Gender:Male

Posted 30 September 2012 - 08:35 PM

If your pH tends to stay high, then just add more acid and your TA will continue to get lower and at some point your pH should not rise so much. You can go down to a TA of 50 ppm if necessary. If you find your pH more stable, even if the pH settles in a little higher such as 7.7 or 7.8, then that's fine. You can then use 50 ppm Borates at that point for further pH buffering.

#20 waterbear

waterbear

    Village Idiot ;)

  • Moderators
  • PipPipPipPipPip
  • 3,279 posts
  • Gender:Male

Posted 01 October 2012 - 08:33 AM

What is your sanitizer level when you are testing pH? Are you using chlorine or bromine? HIgh santizer levels can cause a chemical interference with the pH test and cause it to read high when it is not.
Also, the main cause of pH rise in a tub is outgassing of CO2 from the aeration from the jets and bubblers so often a very low TA is needed along with the addition of 50 ppm borate to introduct a boric acid/borate buffer system.

OK - so I'm attempting to lower the pH with Muriatic Acid and have brought it down - it's now right around 8 - I know I need to get it to ~7.2 but now my TA is below the target of 100-120. According to the test kit I purchased - TA is at about 90



Bottom line is this, if your pH is constantly rising (from outgassing of CO2 then your TA is too high.I am not sure why you are attempting to maintain a TA of 100-120, that is WAY to high for a spa!!!! Even 90 ppm is too high in most cases in a chlorine spa and TA as low as 50 ppm in not unheard of to maintian pH stability.
If you were using MPS and organic bromine then a higher TA would be warranted since both are more net acidic than dichlor and the pH rise from increased CO2 outgassing would offset the constant acid 'additions' from these chemicals.
I've tested more water than I ever care to think about!
Board Moderator

#21 waterbear

waterbear

    Village Idiot ;)

  • Moderators
  • PipPipPipPipPip
  • 3,279 posts
  • Gender:Male

Posted 01 October 2012 - 10:29 PM

There is a lot of misinformation entrenched in the industry that is NOT based on sound water chemistry TA levels are a prime example because most folk in the industry really don't understand what TA is and what it does. In a pool or spa TA is mostly carbonate alkalinity (sometimes called carbonate hardness) and is mostly in the form of bicarbonate at normal pool pH with (in equilibrium with carbonic acid, which for our intents and purposes is basically CO2 dissolved in the water. The higher the TA the higher the bicarbonate level and the higher the dissolved CO2..The higher the disoolved CO2 the faster it will outgas (even faster with the aeration from the jets and bubblers) and outgassing of CO2 is the MAIN cause of pH rise in pools and spa. However, most people in the industry don't understant this simple fact so you now know MORE about pool and spa water chemistry than most people in the industry! ;) B)
I've tested more water than I ever care to think about!
Board Moderator

#22 waterbear

waterbear

    Village Idiot ;)

  • Moderators
  • PipPipPipPipPip
  • 3,279 posts
  • Gender:Male

Posted 03 October 2012 - 11:53 PM

no but if the santizer was low something could start growing in the tub and create a big chlorine demand.Never assume, TEST!
I've tested more water than I ever care to think about!
Board Moderator

#23 waterbear

waterbear

    Village Idiot ;)

  • Moderators
  • PipPipPipPipPip
  • 3,279 posts
  • Gender:Male

Posted 04 October 2012 - 08:54 AM

high sanitizer levels can interfere with some other tests (it can causes false high pH readings and can bleach out the dyes in the mixed indicator in the TA test causing the color change to go from blue to yellow instead of green to red or fade the colors of the indicator in the CH test--however, the results of these two tests are still vaiid, just harder to read) but if the sanitizer is testing low and you are using an FAS-DPD test (drop counting), OTO test (color comparator with yellow color blocks), or FC test strips that turn to shaded os purple (NOT pink or red)then if they test indicated low sanitizer, it is low!

IF you are using DPD testing (color blocks on comparator or strips are shades of pink or red) then high santizer levels CAN bleach out the test if the sanitizer is high and make you think it is low.


This is why the general consensus here is to recommend the Taylor K-2006 with the FAS-DPD chlorine test or the K-2106 FAS-DPD kit for bromine. IF the sanitizer is testing low it is low (up to almost about 50 ppm FC even though Taylor says 20 ppm. In actual practice it has been reported that it is useful at very high FC levels if you add additional DPD powder. The initial scoop or two will 'flash' pink and then beach out but after an additional scoop or two the pink will "hold" and you can titrate.)
I've tested more water than I ever care to think about!
Board Moderator

#24 Orion6192

Orion6192

    Spa Savant

  • Members
  • PipPipPip
  • 94 posts

Posted 07 October 2012 - 07:06 AM

When it refers to adding "x" oz of a chemical like dry acid... Is that by weight or volume. Usually liquid is volume - you put water in a measuring cup and you can see 1 oz. do you weight the dry acid, like with a scale?

#25 waterbear

waterbear

    Village Idiot ;)

  • Moderators
  • PipPipPipPipPip
  • 3,279 posts
  • Gender:Male

Posted 07 October 2012 - 09:13 AM

Dry chemicals are generally by weight. Because of differences in densities of different chemicals 1 oz by weight might not be the same as 1 oz (2 tablespoons) by volume). I use an inexpensive kitchen scale (such as this) for measuring chemicals..
IF the container gives a volume measurement for a certain PPM increase (such as adding 2 teaspoons per 300 gallons or something like that or specifies fluid ounces and not just ounces) then you can follow that but if it just give a measurement for a dry chemical in in ounces, pounds, or grams then it is weight. You can weigh out a known amound of a chemical and you might find that, for example, there are about 4 teaspoons of a certain dry chemical in, say, a half ounce so in the future you could measure THAT chemical by volume. However, be aware that if the manufacturer changes suppliers the volume measurement could change.
I've tested more water than I ever care to think about!
Board Moderator

#26 Orion6192

Orion6192

    Spa Savant

  • Members
  • PipPipPip
  • 94 posts

Posted 09 October 2012 - 04:51 AM

"Also, the main cause of pH rise in a tub is outgassing of CO2 from the aeration from the jets and bubblers"

So whe you test you pH, does it matter when you test it? It seems... And I'm only have a short window of knowledge on this, is that right after a 20 min full aeration cycle the pH will be higher that if youlet it "rest" for awhile after the run cycle.

Is this correct?

I dropped my tub last night from 8.0 pH and 150 TA. I could not get much movement in pH,only TA. I let it set over night and its 7.4 -7.6 (drop test) this am and TA looks to be about 40-45 (test strip - didn't have time to drop test it). My FCC was 7.5ppm and this am looked to be 5-6 via test strip.

So, if I run the tub will my pH pick up and then settle down,or just pickup and stay up?

#27 Orion6192

Orion6192

    Spa Savant

  • Members
  • PipPipPip
  • 94 posts

Posted 09 October 2012 - 02:20 PM

Full post of numbers using the Taylor drop tests:

pH=7.5
FC=2.0
CD=.2
TA=60
CH=190
CYA=30-35

Time to switch to bleach. What about my CH?

Using the dropping TA method really got my number more inline. Took sometime and a lot of acid but wow...

Thanks!


#28 chem geek

chem geek

    Wizard of Water

  • Members
  • PipPipPipPipPip
  • 4,800 posts
  • Gender:Male

Posted 09 October 2012 - 04:26 PM

Your CH is fine. Usually you target 120-150 ppm to avoid foaming, but your 10 is OK since you've got your pH and TA down now.

Aeration raises the pH with no change in TA, but it doesn't "settle back down". However, if the water isn't getting thoroughly mixed, then if you measure near the surface you can measure higher than the average pH of the bulk water. If you are aerating using jets and circulation, this usually isn't a problem. The aeration is driving off carbon dioxide faster and that's also occurring faster at a lower pH which is why the procedure lowers the pH and aerates the water. When you add acid, you lower both pH and TA. So the net result of the process is a lowering of TA.

ACTIVITY .......... pH .... TA ... The following assumes 6.8 is the lowest measurement on the pH test kit
======================

Acid ..................... - ........ - ... Add enough acid to bring pH down to 7.0 (if it's already there, then just skip to the next step, aeration)

Aeration ............. + ....... 0 ... Aerate until pH rises to 7.2
Acid ..................... - ........ - ... Add enough acid to bring pH down from 7.2 to 7.0 (you may continue to aerate while you do this)
-------------------------------------
Aeration & Acid .. 0 ....... - ... Continue this combination (cycling of the two above) until TA is at the target you want

then AFTER you have reached your target TA,

Aeration .............. + ....... 0 ... Aerate until the pH rises to your target pH (say, 7.5).

======================
Net of Above ....... 0 ........ -

#29 chem geek

chem geek

    Wizard of Water

  • Members
  • PipPipPipPipPip
  • 4,800 posts
  • Gender:Male

Posted 15 October 2012 - 09:49 AM

If the pH is rising due to outgassing then the TA is too high so you WANT it to get lower. TA is a SOURCE of rising pH. If you really want to raise the TA back up, then you add baking soda, but that will just keep you in a vicious cycle of acid addition with baking soda addition. To break out of that cycle, let the TA drop lower. For a spa, having a TA of 50 ppm is not unreasonable. For additional pH buffering, you can use 50 ppm Borates (from boric acid; it's what is in Proteam Gentle Spa).

#30 Dave_J

Dave_J

    Newbie

  • Members
  • Pip
  • 6 posts

Posted 31 October 2012 - 08:58 AM

What, exactly, is the "dry acid" product that is referenced here? Is it just packaged as pH Decreaser?

#31 chem geek

chem geek

    Wizard of Water

  • Members
  • PipPipPipPipPip
  • 4,800 posts
  • Gender:Male

Posted 31 October 2012 - 11:55 AM

Yes, "dry acid" is sodium bisulfate that is commonly sold as "pH Down" or "pH Decreaser" or names like that.

#32 Dave_J

Dave_J

    Newbie

  • Members
  • Pip
  • 6 posts

Posted 01 November 2012 - 05:27 AM

Thanks chem geek. I've been a tub owner for 2 years, and haven't paid a lot of attention to chemistry... fortunately, the tub has remained pretty nicely clean with the dosage of dichlor I've always given after each use (just my wife and I). However, coming across these threads makes me think I've been VERY lucky. I have the Taylor on order, and intend to get a strict regimen going when it gets here.

#33 Orion6192

Orion6192

    Spa Savant

  • Members
  • PipPipPip
  • 94 posts

Posted 11 November 2012 - 01:51 PM

Okay... Need some clarification.

Your example is 300ppm and pH greater than 7.8. You calculated 19oz... How? The pool calculator won't tell you this.

Anyway, I have a 340 gallon fresh fill. I thought I would balance it first this time.

My TA was 200 and my pH was 7.2.

I calculated incorrectly and started with 7.6 oz (I did a ratio of 300 over 240 = 19 over X and got 15.2). Ran full jets, air, etc and it dropped to TA of 130 and pH went to 7.8.

According to the chart at the top, I need to go to step 2 and recalculate my amount needed. You example shows you going from 1 cup to 6oz to 3, then 2 then 1 even though your pH is greater than 7.8.

I recalculated and came up with adding 4.12 oz (half of 8.23) and did it again. This time I got a TA of 125 and pH of 7.8. So in this scenario I would got to step 2 and recalculate. This time I would use 2.57 oz (half of 5.145).

Is this last step correct assuming 100 over amount to reduce = 8 over "X"

100,,,,,,8
----- = ----
65,,,,,,,X

Thanks... I have not added dichlor yet... So it straight town water.

Starting numbers from the tap.

PH 7.2
FC 1.2
TA 200
CH 240

#34 chem geek

chem geek

    Wizard of Water

  • Members
  • PipPipPipPipPip
  • 4,800 posts
  • Gender:Male

Posted 12 November 2012 - 11:17 AM

If you scroll down to the "Effects of adding chemicals" section in The Pool Calculator you will see how much adding acid lowers the TA. For your 340 gallon spa (entered after "Size" at the top of the page), 117 ounces of dry acid lowers the TA by 1001 ppm so 1.17 ounces weight (0.78 ounces volume or 4.7 teaspoons) lowers it by 10 ppm (I use scaled up values to get more decimal places -- otherwise, you see that 1.17 to 1.22 all say 10 ppm). The amount of TA drop from acid is independent of pH.

If you do the calculation using 350 gallons and 240 ppm TA from Nitro's write-up, you get 29 ounces weight which is about 19 ounces volume (you can see that ratio in the "pH" section for dry acid).

In 340 gallons, your TA drop of 70 ppm implies 7 ounces weight or 4.7 ounces volume of dry acid. Was your 7.6 ounces weight or volume?

Don't overthink the procedure. It cuts in half for each step just to reduce the possibility of going too low in pH for too long. So you don't need to worry about your initial amount. Just see how much TA you have left to go and add half the required acid amount.

#35 Orion6192

Orion6192

    Spa Savant

  • Members
  • PipPipPip
  • 94 posts

Posted 12 November 2012 - 02:47 PM

I was doing weight... Is that correct?

I see in the calculator that 7oz in 340 reduces TA by 60. Is the 7oz by weight?

My number tonight after tweaking are TA50 and PH 7.6, ran another 20 minutes (1cycle, no adjustment) and TA 50 and PH 7.8. (Sunday)

My FC is 7.6 today, 24 hours after dosing it with Dichlor to 10ppm. (Monday)

It was a new tub,one month old, so we dumped the water even though it was crystal clear. We used SeaKlear first and wow... What a scum line. Not horrible, just unexpected. Will be doing the bleach / dichlor method again.

I don't dare go lower than TA of 50 do I?

Side note... How much Gentle Spa do I add to get to 50ppm in a 340 gallon tub? I get 13oz but thats using Boric Acid as the chem. from the App.

(Tuesday)?Didn't add Gentle Spa yet, waiting on confirmation for amount. But tonight's numbers are TA 50 PH 7.6 and FC 5.2.

Tub has has no use since I filled it. I want to balance it first. Is it okay to add the Gentle Spa now. I'm not sure if I'm balanced or not.

Thanks....

#36 chem geek

chem geek

    Wizard of Water

  • Members
  • PipPipPipPipPip
  • 4,800 posts
  • Gender:Male

Posted 13 November 2012 - 05:48 PM

Yes, that was correct. Your 7.6 ounces is close to the 7 ounces weight that was expected. The Pool Calculator "Effects of adding chemicals" uses weight. The only place you see volume is in the upper sections where it shows both saying things like "# by weight or # by volume of dry acid".

50 ppm TA should be good. The instructions for ProTeam Gentle Spa say 4 ounces (weight) per 150 gallons so for your 340 gallon tub that's 9.1 ounces weight. They may not be going up to 50 ppm -- they are probably going to around 30-40 ppm. I'd just use 13 ounces since they say one can add 2 ounces per 150 gallons in between drain/refill cycles so that's a total of 6 per 150 gallons or 13.6 ounces for 340 gallon.

You can add the Proteam Gentle Spa now since you've got a good water balance. Some people report the pH rising right after adding this product so you might have to add some acid to lower it. With pure boric acid, that won't happen and it's instead slightly acidic.

#37 Orion6192

Orion6192

    Spa Savant

  • Members
  • PipPipPip
  • 94 posts

Posted 16 November 2012 - 01:27 PM

I went with 12oz (2-6oz packs). I'm not clear on how you got to 13 oz with the 2oz every 150 gallons. I would get closer to 10 and that would seem like it would give you 60ppm. I hope I'm wrong in my math because using boric acid it tells me 13oz.

I was 7.5,pH and 50ta. I'll report after my tub cycles for a bit what it jumps to.

After Gentle Spa:

TA 70. pH 8.0+

I dialed it down to 50TA and pH settled in at 7.8 for 2 cycles. If I don't get in I bet it would be 7.6 in a while. But, we're gonna hop in and enjoy our tub.

Let me know if something seems off with what I did...

Thanks -

Scott

#38 chem geek

chem geek

    Wizard of Water

  • Members
  • PipPipPipPipPip
  • 4,800 posts
  • Gender:Male

Posted 16 November 2012 - 04:46 PM

50 ppm borates in 340 gallons is 13 ounces weight (14 ounces volume) of boric acid. The Gentle Spa recommended initial amount is probably not for 50 ppm borates. Anyway, what you've got is fine.

#39 chem geek

chem geek

    Wizard of Water

  • Members
  • PipPipPipPipPip
  • 4,800 posts
  • Gender:Male

Posted 19 December 2012 - 07:11 PM

First off, I would have used bleach instead of Dichlor so that you wouldn't be increasing your CYA level.  For every 10 ppm Free Chlorine (FC) added by Dichlor, it also increases Cyanuric Acid (CYA) by 9 ppm.  As the CYA gets higher, then for the same FC level the active chlorine level is lower so disinfection and oxidation rates go down.  For simplicity, think of the active chlorine level being proportional to the FC/CYA ratio.

 

Breakpoint chlorination is wrong if you are talking about the 10x rule.  The rule came from the breakpoint chlorination of ammonia by chlorine, NOT of Combined Chlorine (CC) by chlorine.  Ammonia is measured in ppm N (Nitrogen) units while chlorine and combined chlorine are measured in ppm Cl2 (molecular chlorine) units and there is roughly a factor of 5 difference between these.  The oxidation formula has 3 chlorine for every 2 ammonia, so a ratio of 1.5 to 1 so multiplying by the factor of 5 one gets 7.6 (using the exact numbers) and due to side reactions and needing to get over the hump of the first reactions, in practice it's 8-10x from which the "10x rule" was born.  Problem is, that combined chlorine is already in chlorine units so that's a factor of 5.  Combined chlorine also already has 1 of the 1.5 chlorine needed.  So in terms of chlorine demand, and accounting for organic combined chlorine and not just inorganic combined chlorine, the rule is no more than 3x.  Even then, using more just makes things go faster and using too little just means you can add more later as nothing gets "stuck".

 

OK, back to what you saw.  I suspect you had ammonia (originally; now monochloramine) or organic precursors (such as urea or creatinine) in your water.  Had you left your initial water alone, the FC would have dropped and the CC might have gone up but for CC it depends on what type.  Anyway, you had something in the water that consumed FC.  So the FC you added partly oxidized some of the CC, but it also reacted with precursors to form more CC that was then oxidized.  What you need to do is to keep shocking with chlorine until your 24 hour chlorine loss rate is around 25% if the water is fairly new and you don't have an ozonator (with an ozonator or with older water the loss rate may be 50% or more).

 

Now part of the problem is that your CYA is high.  As I mentioned, this slows down chlorine reactions because most of the chlorine is bound to CYA.  So it's easier for your spa to "get behind" from bather load because the chlorine isn't able to oxidize it fast enough due to the high CYA level.  So if you use your spa regularly, then you are continuing to add chemicals to the spa that need to get oxidized, but the active chlorine level is too low so such chemicals build up as does CC.  This is why we recommend the Dichlor-then-bleach method since after an initial 30-40 ppm or so of CYA, the subsequent bleach prevents the CYA from rising.  You add Dichlor about once a month to make up for a slow loss of CYA, but basically you keep it fairly constant so that the active chlorine level remains fairly constant.  Also, you make sure you add enough chlorine after each soak to handle all the bather waste; many people simply don't add enough.  We have rules-of-thumb for how much to add, but you really just add whatever is needed so that you measure at least 1-2 ppm FC for the start of your next soak (or 2-4 ppm FC 24 hours after adding the chlorine, if you don't soak every day; you then need to add more chlorine in between soaks to maintain its level though can let it drop to 1-2 ppm FC just before your next soak).



#40 chem geek

chem geek

    Wizard of Water

  • Members
  • PipPipPipPipPip
  • 4,800 posts
  • Gender:Male

Posted 20 December 2012 - 06:39 PM

Yes, since your CYA is already up, use sodium hypochlorite (chlorinating liquid or bleach) to raise the FC up.

 

As for routine maintenance, you need to MAINTAIN a disinfectant level in your spa at all times and unfortunately chlorine won't last more than a few days.  So you'd have to add it every day or two or if you raised it to a higher level then perhaps once or twice a week (though such raising will be harder on the hot tub cover).  The chlorine system is not designed for spas that are not used every day or two or at least twice a week.  If you want to use chlorine, then you should look at getting the ControlOMatic TechniChlor saltwater chlorine generator so you can have it generate a background level of chlorine between uses.  Some spas have their warranty voided if you raise the salt level to the 1500-2000 ppm needed by this generator.

 

Otherwise, people who use a spa infrequently will often use bromine instead of chlorine because with bromine you can use bromine tabs that slowly dissolve and should last about a week or sometimes two (depending on how many tabs you put into the feeder).  However, bromine and its bromamine by-products smells different than chlorine and some people don't like it.



#41 chem geek

chem geek

    Wizard of Water

  • Members
  • PipPipPipPipPip
  • 4,800 posts
  • Gender:Male

Posted 21 December 2012 - 10:26 PM

If you want to convert to bromine, you can do so without changing the water.  It's converting from bromine to chlorine that requires a water change.  To convert from chlorine to bromine, you just add sodium bromide and start using bromine tabs.  Since you don't know if you would like bromine, perhaps you can try it in the spring so if you don't like it you can go back to chlorine with a water change.



#42 chem geek

chem geek

    Wizard of Water

  • Members
  • PipPipPipPipPip
  • 4,800 posts
  • Gender:Male

Posted 24 December 2012 - 11:52 PM

It is not true that unstabilized chlorine in household bleach will not last long once diluted in the tub water because you already have CYA in the water that stabilizes it.  If you were referring to bleach going bad when concentrated, that does happen but it's usually not very fast for quality bleach.  It's more concentrated chlorinating liquid that degrades about 4 times faster.  Of course, any concentrated sodium hypochlorite chlorine left in hot temperatures will degrade faster.

 

The only way to lower the CYA level is through water dilution.  It does degrade slowly over time, but around 5 ppm CYA per month at hot spa temperatures so not very fast.



#43 chem geek

chem geek

    Wizard of Water

  • Members
  • PipPipPipPipPip
  • 4,800 posts
  • Gender:Male

Posted 28 December 2012 - 01:11 AM

If you had no CYA in the spa water at all, then adding unstabilized chlorine will outgas faster, that is true.  And of course if it's exposed to sunlight it will break down rather quickly losing around half every hour.  This is why it's the "Dichlor-then-bleach" method and not the "bleach only" method.  The CYA is needed to reduce the active chlorine level which reduces the rate of loss from outgassing and reduces its strength of oxidizing skin, swimsuits and hair as well as harshness on equipment and covers.

 

Oh, 2 years old is quite old.  I didn't realize that it was so old.  6% bleach can last for many months, even a year if kept out of hot temps, but 2 years is most definitely pushing it.  The table at the bottom of this post will give you some idea of how quickly various concentrations of bleach or chlorinating liquid lose half their strength at various temperatures.

 

The high CYA level lowers the active chlorine level so this means with the usual FC levels the chlorine reacts more slowly.  With a higher bather load you could get behind in trying to oxidize bather waste.  If you only soak once or twice a week, you might be OK, but if you soak every day or two you could find that the chlorine is not able to keep up and eventually your water may turn dull/cloudy.  The disinfection rate is also lower, though most bacteria are easy to kill.  With very high CYA, somewhere well above 100 ppm, there seems to be more likelihood for getting hot tub rash/itch from Pseudomonas aeruginosa.  So you can just chance it since perhaps your CYA isn't much over 100 ppm.  Up to you.  This will certainly get fixed on your next water change or you can do a partial drain/refill if you don't want a complete one.



#44 chem geek

chem geek

    Wizard of Water

  • Members
  • PipPipPipPipPip
  • 4,800 posts
  • Gender:Male

Posted 28 December 2012 - 11:28 PM

Yes, it would be better to use bleach now since your CYA is already high.  Don't use any more Dichlor until your next water change.



#45 chem geek

chem geek

    Wizard of Water

  • Members
  • PipPipPipPipPip
  • 4,800 posts
  • Gender:Male

Posted 29 December 2012 - 01:22 PM

Your mind isn't feeble.  You're doing great!



#46 Craddock02

Craddock02

    Newbie

  • Members
  • Pip
  • 6 posts

Posted 09 February 2013 - 01:46 PM

I posted this earlier under my old forum name and somehow got black listed so I'm back, asking 2 questions;

 

For the admin;

1 - why was I banned from this forum? I reported some responses to this thread as spam and then I'm out? I've sent the admin multiple emails asking this question and have yet to receive a response. If it turns out that the spam cam from me I would like to know because then it would mean that my computer has been compromised and I would get it cleaned...

 

For anyone else;

2 - my original question - when I add Dichlor to my hot tub - I like to have it predissolved - thinking this helps it circulate and become homogenous. Everything (OK almost everything) dissolves a lot faster in hot water. So I add the granules to water that I get from a hot water dispenser on my sink (160-180F). Will this hot water cause the dichlor to degrade or cause problems?

 

 

Lastly for the admins; If you access this site by searching “pool and spa forums” in Google Chrome using McAfee Antivirus, your site shows up as being unsafe. Apparently your SiteLockSecure program isn’t playing well with McAfee. Remember this is coming from someone that has been blacklisted from your site for some reason. I have a screen shot if anyone cares to see it...



#47 chem geek

chem geek

    Wizard of Water

  • Members
  • PipPipPipPipPip
  • 4,800 posts
  • Gender:Male

Posted 10 February 2013 - 01:12 AM

The Dichlor in hot water will be OK for a short time.  It would be an issue over days, mostly in increased chlorine outgassing and increased rate of oxidation of CYA by chlorine (so yes, that can be considered to be breakdown of the Dichlor).  Are you sure your hot water tap is 160-180ºF?  Even at 140ºF it only takes 3 seconds for a 2nd degree burn and 5 seconds for a 3rd degree burn.



#48 Craddock02

Craddock02

    Newbie

  • Members
  • Pip
  • 6 posts

Posted 23 February 2013 - 05:35 PM

Well - I'm not using the hot water any more - going to try without it since each week the chlorine level is almost at zero. And to answer your question; it is not my hot water tap. It is a hot water dispenser for making tea, instant coffee, oatmeal... It is safegarded in as much the lever is on the back side where it can't be inadvertently activated. It is mounted on the back of thie sink. I checked it after you asked since I knew it was up there but had no idea how hot. I used a non contact IR thermometer and it is 183 F. So yes - it could burn quickly.



#49 Orion6192

Orion6192

    Spa Savant

  • Members
  • PipPipPip
  • 94 posts

Posted 21 July 2013 - 08:45 AM

Yes, that was correct. Your 7.6 ounces is close to the 7 ounces weight that was expected. The Pool Calculator "Effects of adding chemicals" uses weight. The only place you see volume is in the upper sections where it shows both saying things like "# by weight or # by volume of dry acid".50 ppm TA should be good. The instructions for ProTeam Gentle Spa say 4 ounces (weight) per 150 gallons so for your 340 gallon tub that's 9.1 ounces weight. They may not be going up to 50 ppm -- they are probably going to around 30-40 ppm. I'd just use 13 ounces since they say one can add 2 ounces per 150 gallons in between drain/refill cycles so that's a total of 6 per 150 gallons or 13.6 ounces for 340 gallon.You can add the Proteam Gentle Spa now since you've got a good water balance. Some people report the pH rising right after adding this product so you might have to add some acid to lower it. With pure boric acid, that won't happen and it's instead slightly acidic.


Being that we now know Pro Team Gentle Spa raises the pH - would it not be wise to just add the gentle spa at the beginning of the process and lowering the pH with dry acid all at one time or is it not that simple? Will It through other numbers off?

#50 chem geek

chem geek

    Wizard of Water

  • Members
  • PipPipPipPipPip
  • 4,800 posts
  • Gender:Male

Posted 22 July 2013 - 01:43 PM

It's harder to move the pH once the borates are added, so I would just keep the pH low and aerate the water while adding acid to lower the TA, but then instead of raising the pH once the TA is reached, then use the ProTeam Gentle Spa to add the borates. If the pH still overshoots, just add some acid to compensate.






1 user(s) are reading this topic

0 members, 1 guests, 0 anonymous users

website security