How to increase TA without affecting pH?

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Daf-Tekno

Daf-Tekno

0
Sep 14, 2014
90
Calgary / AB
I have my TA where I want it bit my pH is way too high.

Muriatic acid will lower the pH but it will also lower the TA.
Baking Soda will raise the TA back up again, but will also raise the pH!

How do I lower pH without lowering TA?
Or, put another way, how do I increase TA without increasing pH?
 
You are missing the fact that TA is a source of rising pH so you don't want it as high as 100 or even 80 in a spa. If you are going to be using a hypochlorite source of chlorine, then you want your TA significantly lower, such as 50 ppm, and can then use 50 ppm borates as an additional pH buffer.

The general rule is that if your pH is rising over time, then lower your TA level. TA is mostly a measure of bicarbonate in the water so is a measure of the over-carbonation of the water. Carbon dioxide outgases and this causes the pH to rise with no change in TA.

You should read the sticky How do I use Chlorine in my Spa?. Note that your CYA level is on the high side for a spa -- 30-40 ppm is a better sweet spot unless your spa is uncovered and exposed to lots of sunlight all day long. Note that if you add chlorine after a soak to handle the extra bather load, if your SWG is set to only handle background dosing, then you should be adding bleach and not Dichlor chlorinating granules. For every 10 ppm FC added by Dichlor, it also increases CYA by 9 ppm.
 
Hi y'all,

The SWG (ChlorMaker IL) manual recommends CH of 300 - 400, so I've chosen 300 to be on the safer side.
It also recommends TA 80 - 120, so again I've chosen the figure that is closest to the recommendations on this forum (i.e. 80).

You can see that I'm trying to conform to what they recommend is best for the SWG hardware, and also what you guys recommend for spas / pools in general.
This is difficult, as they want the CH & TA much higher than what you guys want me to be operating at.

Having a SWG, and according to the Chlorine-CYA chart on this forum, my CYA levels need to be 60 - 80.
No figures are given below 60 for SWG systems, thus I conclude such levels are not recommended or simply don't work.

If such lower levels do in fact work, maybe they could be added / amended to this chart so I can use it.
Or at least, maybe you guys could tell me the missing Min FC / Max FC / Algae / Shock / Algae Shock figures for CYA levels 0 - 50 for SWG systems.

I finally got my water stabilised last night, after many long evenings with the test kit.
Now it looks like all my hard work may have to be thrown away, if I gotta drain and refill my hot tub to conform to these new revelations.

Bit of a shame, when I've tried to be as wise as possible, and tried to read & combine related threads of 'How do I use Chlorine in my Spa', borate use, CYA vs chlorine for SWG and the BBB system.

Yes, Chem Geek, I read and printed out the 'Chlorine use in Spas (Pools)' post, condensed and combined the relevant data into my current quick-reference sheet for my BBB / SWG / Borate hot-tub.
But, as mentioned, some data had to be altered to conform to Controlomatic's specifications for their SWG system.

Similarly, on posts here the salt levels should be 3000 - 3500, but the ChlorMaker operates at very different levels of 1500 - 2000, so again doesn't conform.

I hope I'm right in thinking that Controlomatic's specifications / requirements for the correct use of their SWG system takes priority over recommendations given here.
Or are they giving out figures that err massively on the side of caution, and can be overridden by your suggestions without any worries of wrecking my SWG's hardware..?

I'll fire them off another e-mail asking if I can conform to your much lower CH & TA levels (without mentioning you guys specifically).

Not easy to get all this right, I can tell you!

Regards,
D
 
You can't mix our advice and other sources of advice, that is sure to lead to problems. Pick one and stick with it.

I suspect they just copied other rather old suggestions for chemical levels and didn't bother to adjust them for their specific situation. Those numbers look very much like the outdated pool level recommendations that we see from many many source. Regardless, it is my opinion that following their recommendations will lead to problems. At that TA level, you will have very rapid PH rise when the spa jets are running and combined with the CH levels that is likely to lead to calcium scaling.

Calcium does nothing to help out SWG hardware. As far as the SWG is concerned it is best if the CH level is near zero. If anything medium to high calcium levels risk damaging the SWG, as SWG cells are very prone to calcium scaling at higher CH levels. Short term, calcium scaling in the SWG is annoying, longer term it will reduce your cell lifetime. Calcium around 120 to 150 is useful in a spa for other reasons and not a noticeable risk for the SWG, so you don't actually want CH near zero, even though that is what is best for the SWG.
 
Hi Jason Lion,

I'm not mixing advice. It is based on the figures given on this forum:

http://www.troublefreepool.com/content/134-recommended-levels

Fiberglass with SWG
FC 3-5 (See chart)
pH 7.5-7.8
TA 60-80 (ChlorMaker recommends 80 - 120, so both agree that 80 is good, no?)
CH 220-320 (ChlorMaker recommends 300 - 400, so both agree that 300 is good, no?)
CYA 70-80

Trying to be wise, I've found levels where both you and Controlomatic agree are acceptable.

But now it seems that TA of 80, CH of 300 and CYA of 70 are all far too high.
So why do you give these values as "Recommended Levels"?

Are these values in your "Recommended Levels" chart themselves outdated, like you suggest Contolomatic's figures are?

Before I drain the tub yet again, can you confirm which set of data is correct, the figures given in this thread or those given in the "Recommended Levels" chart.

As frustrating as my situation is, I greatly appreciate your guys' assistance in this and hope to resolve it before long.
Many thanks - D
 
I see the confusion. You are taking numbers from the recommended levels article in Pool School. It probably doesn't say so explicitly, but that is a set of swimming pool recommendations. Everything in Pool School assumes swimming pool. Spas are similar, but there are some important differences. Swimming pool numbers are not really the same as spa/hot tub numbers. For a spa you want to start with this sticky, admittedly a little more difficult to find, but much more appropriate for a spa/hot tub.
 
The numbers are for a pool. Hot tubs are hotter and more susceptible to scaling because the higher temperature increases the csi. Hot tubs are usually surfaced in acrylic which does not need calcium.
 

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I have a swg spa and you should be careful with ch over 100, I have replaced two blades due to being completely eroded by calcium scaling. One blade was non existent and the store I bought it from years ago always recommended ch around 300 to avoid bubbling.
 
Though you could have your CYA higher with a proportionately higher FC just as is done in SWG pools, there is no need for that in a spa because 1) it is usually covered so does not have chlorine loss from sunlight exposure, 2) the water volume is far lower than in a pool so the SWG units are not usually woefully undersized so can keep up with the chlorine loss rate, and 3) most people don't want to start their soak with 4 ppm FC since that will smell more of chlorine and chloramines. So as described in the sticky How do I use Chlorine in my Spa?, the CYA level can be lower (the sticky says 20-30, but since CYA slowly degrades I now usually tell people 30-40 and then replenish the lost CYA once a month with a day of Dichlor use). Unlike a pool, a covered spa usually doesn't get algae but I'd still have the minimum FC level in between soaks be no lower than 5% of the CYA level as is done for SWG pools.

Usually one wants to start one's soak with 1-2 ppm FC and not much higher in order to avoid smelling chloramines during the soak. Then, one doses after their soak in proportion to their bather load. The SWG would then just be used to provide a background level of chlorine in between soaks. Though one could use the "boost" mode in some spa SWG systems, that will have the SWG wear out faster and the "boost" mode isn't usually scalable and may not be enough for higher bather loads. Adding chlorine bleach in the proper proportion is often a better approach.

As for how much bleach to add, that depends on what else you have in the system. With an ozonator, it will oxidize some of the bather waste so less chlorine needs to be added. Whereas without an ozonator the rough rule-of-thumb is that every person-hour of soaking needs around 3-1/2 teaspoons of Dichlor or 3-1/2 fluid ounces of 8.25% bleach or (when using Nature2 with silver ions) 7 teaspoons of non-chlorine shock (43% MPS), with an ozonator the needed dose is around half these amounts though obviously that depends on the strength of the ozonator. The real rule to use is to add whatever is necessary so that the chlorine level never gets too low between soaks where I'd say too low would be below the 5% of CYA level.
 
Hi again,

Setting up my tub again, and again the same issue.

High pH with low TA. pH 7.8 & TA 40.
(CH 100, CYA can't check as I've run out of CYA tester in my K-2006 but have added 66% of PoolCalc's recommended dose until I get more tester).

No one seems to have addressed this original question head on, like "To increase TA without raising pH you need to do this...".

All the things that raise TA also raise pH, and to lower the pH again the acid also lowers TA.
Hmmm...

Thanks - D
 
To raise TA with the least effect on pH you use baking soda. If the pH is then too high, you use acid to lower it and the TA will only go down a little unless your pH is very high.

In your situation, you would add 29 grams (around 24 ml volume) of baking soda (sodium bicarbonate) to your 1700 liter spa and that will raise the TA to 50 ppm. The pH would then rise only to 7.84 so will measure nearly the same. You can lower the pH back to 7.80 with only 0.8 ml of Muriatic Acid or 1 gram of dry acid (sodium bisulfate). If you wanted to lower the pH to 7.5, then that would take 10.3 grams of dry acid but the TA will only drop to 47.9 so 48 ppm. So you can see that this really isn't a problem.
 
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