Ph And Ta

[CapMorgan]

Hello all,

I been having a problem with my PH and TA it is always high my water is 2 months old and when ever i balance my water the next day the numbers are high again.

When i balance the water

PH 7.2

TA 100

Because i have a problem with my water just to check to see what is going on the next day my numbers are high again

PH 8.0 or higher

TA 120

I am not trying to micro manage my water but i really feel my numbers should not get that high in 1 day and the odd thing is when my tub was brand new and on my first water fill my PH and TA would always go lower in a week's time since i drained my tub and added new water the water is doing the opposite.

I have been having a problem with my skin with rashes and itching a lot and i really feel that it is because i always have a High PH level can anyone help in why my PH would rise so fast in 24 hours.

CapMorgan

[chem geek]

CapMorgan,

You need to lower the TA in your spa and also target a higher pH of 7.5 or 7.6 or even 7.7. The itching isn't from the pH, but probably with bacteria that causes Hot Tub Itch and that would mean that your sanitation levels are too low. What do you use for sanitation?

To lower your pH, you keep the pH low while aerating your water (just turn on the jets in your spa). This will make the pH rise so keep adding acid to keep the pH low (around 7.0 or so) and measure the TA which you will see drop (at the same pH). When the TA gets to around 70, stop adding the acid and keep aerating which will cause the pH to rise. Stop aerating when the pH is at 7.5. Your TA will now be at 70 and the pH at 7.5 and this will have much less tendency to rise in pH (due to less outgassing of carbon dioxide).

I need to go out for a while so maybe waterbear can respond to you after you give some more details on your spa sanitation.

[CapMorgan]

I Have been using the (Vermont Style) for my sanition which is to use the Dichlor after you are done soaking

I have a 360 gallon tub i use 3/4 of a teaspoon of Dichlor after each soak i also use the nature 2 stick

For my weekly shocking i use 5 1/4 teaspoon of dichlor one week then on the other week i use MPS

The reason why i get my PH down to 7.2 is because it rises so fast it goes from 7.2 to 8.0 or higher with in a 24 hour period i do add 16 ouches of Pro team PH down to get my PH to 7.2

I will do what you say to try and get my TA down to 70 right now it is as 120

Thanks,

CapMorgan

PS I sure hope this helps as i have not been able to soak for over a week now becuase the itching is so bad

[chem geek]

Well, it turns out I can answer you anyway as I'm back from getting food. I know what the problem is. You cannot use Dichlor as your sole source of sanitation. Dichlor contains both chlorine AND Cyanuric Acid (CYA) and while the chlorine gets used up sanitizing your pool, oxidizing organics, and outgassing, the CYA does not break down and it just builds up. For every 1 ppm FC you increase using Dichlor, you also introduce 0.9 ppm of CYA. The CYA will reduce the effectiveness of the chlorine so after a few uses, the chlorine will no longer be able to disinfect your spa.

So, what you need to do is replace your spa water, then use Dichlor for a few times in the spa and stop using Dichlor when you have added enough for 20 ppm FC. Then, use regular (or Ultra) unscented bleach as your sanitizer from then on until you change the water again in about a month (or whenever you change your water).

Oh, and since you will have to replace your spa water, don't bother with lowering the TA. Just add less baking soda (sodium bicarbonate) when you replace your spa water so you just get to 70 ppm TA. And last, but not least, do not use Dichlor for shocking -- use bleach instead. You don't want your CYA level to get much above 20 ppm and you'll want to maintain an FC level of at least 4 ppm minimum.

I looked up this "Vermont Method" which just uses Dichlor after every use and for shocking and that is a terrible, terrible method, due to the buildup of CYA -- especially for a spa that needs higher disinfection levels since the bacteria that causes hot tub itch is hard to kill.

[CapMorgan]

Chem Geek

Ok i will do a water change when the weather permits, I live in the midwest and am concerned about the cold during a water change.

Couple more questions for you about using bleach as for sanition. My owners manuals says never never use bleach in the tub so should i be concerned about that?

1. should i use bleach as a daily sanition like dichlor and should i add it before or after i soak and how much bleach should i use for a 360 gallon tub.

2. when doing my weekly shock how much bleach should i use for my tub?

3. can i still use my nature 2 stick with bleach?

4. On my last and only water fill i did as my tub is new i got 4 months out if it will i still be able to get 4 months out of my water before i have to do a refill?

5. Could i use bromine instead of bleach?

Many thanks for taking the time out to help me out with my problem. Once i get the water changed and balance and i start using the bleach for my sanition i will let you know how that worked our for me.

CapMorgan

[chem geek]

As for never using bleach in your hot tub, that is very very strange since Dichlor produces the exact same hypochloric acid as found in bleach. The only difference is that bleach is more basic/alkaline. When you add the bleach, just take care not to pour it concentrated directly onto any hot tub surface. If you are afraid you can't add it to the water carefully (mixing it with some circulation), you can add it to a bucket of spa water first and then add the bucket of water to the spa.

1. It takes just 3 ounces of 6% Ultra Bleach or 3.5 ounces of 5.25% regular bleach to get to the minimum of 4 ppm FC in 360 gallons. This should be equivalent to 0.35 ounces (weight) of Dichlor. Since you will lose some chlorine between the times you add it, you could add a little more -- say, 5 ounces to get to around 7 ppm FC. With the 20 ppm CYA in the pool (after you use Dichlor a few times), the effective disinfecting chlorine level will only be around 0.16 ppm which should be enough for good sanitation (though it will take about 4 hours to kill the "hot tub itch" bacteria at this level of chlorine, but that should be OK since you aren't using the tub all the time as would be the case with a commercial spa). Try getting your pH to 7.4 before you add the chlorine since it will make the pH rise initially, though it will drop down again as the chlorine gets used (assuming we tackle your carbon dioxide outgassing issue through the lower TA of 70 ppm).

2. Technically, you should not need to do a weekly shock if you maintain proper chlorine levels since breakpoint should occur somewhat continuously. If you have a good chlorine test kit (such as the Taylor K-2006 with FAS-DPD drop test for chlorine), then you can test to accurately see your Free Chlorine (FC) level as well as your Combined Chlorine (CC) level. This latter CC level should be less than 0.5 ppm in which case you don't need to shock. If you do find it higher, then you could shock with 10x the amount of chlorine as the CC measurement (so if CC is 1.0, then use 10.0 ppm FC to shock).

3. I would not use your Nature 2 stick at all. I believe it is just copper (and/or silver) and though that does some disinfection, it obviously wasn't doing you any good for Hot Tub Itch. The chlorine should be plenty for disinfection and oxidation as long as you maintain its level (which it sounds like you would do by daily addition and/or checking).

4. Yes, you can get 4 months out of your hot tub since that is a function of how often you use it. Typically, people that use it every day aren't able to go that long, but this varies by hot tub usage. How do you tell when you need to change your hot tub water?

5. You could use bromine instead of bleach (you would still use bleach to activate the bromide to bromine), but that gets more complicated since there are different kinds of bromine systems you can use. waterbear can tell you a lot more about those options as he is much more familiar with them than I am. I believe you will be happy with using chlorine. It is safe and effective. The main complaint from some people is some chlorine smell, but that is if they use only chlorine without any CYA and you will be starting with Dichlor so will cut down the active chlorine concentration somewhat which will cut down the chlorine smell. With bromine, some people find that it irritates their skin, so try the chlorine first and see how it works for you -- if it doesn't work out, then you can try bromine instead (with help from waterbear). Technically, you HAVE been using chlorine already -- it's just that with Dichlor the CYA in it cut down the effective disinfecting chlorine concentration way, way down after about a week of adding it to your spa so after that you were essentially using your tub with minimal disinfection (which is why Hot Tub Itch bacteria persisted).

[CapMorgan]

H Chem Geek,

Im not sure when i need to change my water i was going by how long the nature 2 stick is good for which is 4 months.

I do have the taylor test kit and i just tested for CYA my water is 2 months old and you wont believe how high my cya is CYA = 100

I will do a dump as soon as i can weather permitting

CapMorgan

[Reese]

... You cannot use Dichlor as your sole source of sanitation....so after a few uses, the chlorine will no longer be able to disinfect your spa....Then, use regular (or Ultra) unscented bleach as your sanitizer from then on until you change the water again in about a month (or whenever you change your water)... I looked up this "Vermont Method" which just uses Dichlor after every use and for shocking and that is a terrible, terrible method, due to the buildup of CYA -- especially for a spa that needs higher disinfection levels since the bacteria that causes hot tub itch is hard to kill.

Greetings Chem Geek and Waterbear!

I'm new to the forum, and I find the advice you are offering here very interesting, mainly because it is a position I haven't seen much of. Most of the information I have accessed makes it seem like dichlor is the conventional method for chlorine sanitation, and that sodium hypochlorite is undesirable due to its low concentration of chlorine, high pH, TDS issues, and short shelf life. In these other sources, CYA is not a concern until it reaches levels above 100ppm, which takes about 3 months in my spa. Most of the dichlor users that post on other forums seem to be able to go 3-4 months or longer with the same water as well, with few reports of decreased sanitizer efficiency, even though their CYA levels must be much above the levels you recommend. I've read a few of each of your posts, but haven't come across any that address the pH and TDS issues, and I'm still not clear on why your CYA recommendations are so much lower than others I've seen. Can you expand on these issues, or direct me to any information that would help me understand the differences in opinion?

Thanks in advance!

Reese

[chem geek]

Reese,

I'm not sure if you will be able to access this link as it is only accessible for U.S. users (non-U.S. IP addresses are blocked from the Pool Forum website due to previous hacking). The issue isn't that you can't use Dichlor up to 100 ppm CYA. It is that higher levels of CYA require higher levels of chlorine for equivalent disinfection. Also, in spas, the bacteria Pseudomonas aeruginosa that causes "hot tub itch" needs much higher levels of chlorine to kill compared to chlorine levels normally achievable in the presence of CYA. This essentially means that you have to limit CYA to low levels in a spa OR if CYA levels are high, then you need to use very high chlorine levels.

This link from the Professional Pool Operators of America (PPOA) also talks about the significant reduction in chlorine's effectiveness when in the presence of CYA.

The best fact sheet that talks about CYA and recommends not using it in spas is found at this link from the Department of Health for Pennsylvania. Even this fact sheet is inaccurate in the way it describes the "weak bond" between chlorine and CYA. The truth is that the bond is only moderately weak or strong such that having higher levels of CYA relative to chlorine (say, 30 ppm CYA and 5 ppm FC) has over 95% of the chlorine bound to the CYA in chemicals that are called chlorinated isocyanurates.

I have a strong interest in pool water chemistry and worked out all the chemical equilibrium equations and species in a spreadsheet that is found at the first link I gave above. The source information for the equilibrium constants may be found on PDF page 18 (document page 12) at this link. I also went to an off-site library to look at the original source document for these equilibrium constants that were determined by scientists in 1973 and presented at a conference in 1974 as follows:

J. O'Brien, J. Morris and J. Butler, “Equilibria in Aqueous Solutions of Chlorinated Isocyanurate”, Chapter 14 in A. Rubin, ed., Chemistry of Water Supply, Treatment and Distribution, 1973 Symposium, (published 1974), Ann Arbor Science, Ann Arbor, MI, pp. 333-358.

In this original source document from 1973, the authors recommend a CYA level of no more than 25 ppm for pools. I have also been in contact with the company that makes Dichlor/Trichlor (Oxy Chemical; Occidental Petroleum) as well as ORP sensor manufacturers. There are financial (economic) reasons that only partial truths and limited information is given with regard to the relationship between chlorine and CYA, but it isn't that the science isn't known. At least that is my opinion of what is going on.

The best information I could find on the CT constant for "hot tub itch" ranges from around 30 to 50 which means that to kill this bug in one minute takes 30-50 ppm FC (or possibly disinfecting chlorine level since the pH was not given for these CT constants). To kill the bug in an hour takes around 0.5-0.8 ppm FC which doesn't sound like much, but you need to understand that CYA significantly cuts down effective chlorine concentration. A rough rule of thumb applicable at a pH near 7.5 and when CYA is at least 5 times larger than FC is that CYA cuts down effective chlorine concentration by a factor equal to the CYA ppm rate. So a CYA level of 30 ppm cuts down the effective chlorine concentration by (more than) a factor of 30. Yes, that is not a misprint -- it's how the chemistry works. Fortunately, most bugs in pools are relatively easy-to-kill so the combination of 30 ppm CYA with 3 ppm FC results in 0.04 ppm of the disinfecting form of chlorine (hypochlorous acid, HOCl) and is equivalent to about 0.1 ppm FC if no CYA were present. This represents an Oxidation-Reduction Potential (ORP) of around 675 mV which is above the minimum 650 mV needed for disinfection, but it takes more chlorine to prevent algae than the 650 mV disinfection minimum. Now for a spa, the hard-to-kill "hot tub itch" bacteria means one should have an effective FC level of at least 0.1 ppm FC if one wants to kill this bug in a 4-8 hours or so (and even that may not be fast enough to overcome normal bacteria growth rates). This corresponds to an FC level of 4 ppm with a CYA level of 20 ppm. This is why I recommend only using Dichlor a few times to have no more than 20 ppm CYA and then to switch to bleach.

As for TDS levels, you have been misinformed. Different levels of chlorine provide different levels of TDS, CH, CYA as shown in the following table that accounts not only for the addition of the chlorine source, but also the using up of chlorine (which is an acidic process) and accounts for the acid or base that must be added to restore pH.

Increase in TDS, Calcium and CYA with 1 ppm FC increase and usage

Type of Chlorine          TDS  CH   CYA  Acid/Base
Bleach / Liquid Chlorine  1.6  0.0  0.0  Slightly Basic
SWG                       0.0  0.0  0.0  Neutral to Moderately Basic*
Calcium Hypochlorite      1.2  0.7  0.0  Slightly Basic
Trichlor (tablets)        1.4  0.0  0.6  Very Acidic
Dichlor (granular)        1.8  0.0  0.9  Moderately Acidic
Chlorine Gas              1.6  0.0  0.0  Extremely Acidic

*SWG varies in its tendency to increase pH and therefore the amount of acid needed to remain neutral. The pH rise (probably from outgassing carbon dioxide due to aeration from the hydrogen bubbles created in the SWG) and added acid to restore pH will increase TDS, but is not shown above since it varies by pool.

Dichlor increases TDS more than bleach (due mostly to the CYA added from Dichlor). Some of the TDS will not be measured by a conductivity meter since some of the CYA is in a neutral form (i.e. is no a charged ion). The TDS from bleach after the chlorine is consumed is in the form of salt (sodium chloride, NaCl). Also, it is a misconception that using bleach or chlorinating liquid is strongly basic/alkaline. Though the initial addition is basic/alkaline, the consumption of chlorine is acidic and these nearly exactly cancel each other out so that the net effect is almost pH neutral. The chemistry involved with this may be found at this link (only accessible in the U.S.). If you look at my first link at the start of this post, you will see that the typical rise in pH found in many pools and spas has to do with the outgassing of carbon dioxide. This is why it may seem like Dichlor is pH neutral when it is not. There are also better ways of keeping the pH from rising as much, namely lowering the TA to as low as 70 or 80 ppm, not trying to force the pH below 7.5, and minimizing aeration (which is hard to do in a hot tub).

As for the shelf life of chlorinating liquid and bleach, this is very much a function of temperature and chlorine concentration (half the concentration lasts 4 times as long), but generally speaking 12.5% chlorinating liquid will lose its strength rather quickly if kept in the sun, but in shade (less than 80F) it will take over 6 months to lose half of its potency (see this link for a useful chlorinating liquid half-life table). In practice, it's a good idea to use chlorinating liquid within a month of its purchase. I have tested the 12.5% chlorinating liquid that I buy from my pool store and it is always at or near full strength, but they keep it in the shade and have good turnover. Bleach in the stores loses its potency much more slowly, as long as it is well capped (sealed). It is more important that you pay attention to the bleach concentration on the bottle as cheap bleaches may only be 2-3% chlorine. Clorox Regular unscented bleach is 5.25% while Clorox Ultra unscented bleach is 6% chlorine.

I don't want to overwhelm you with information, but want you to feel comfortable that the advice of either not using or minimizing the use of products with CYA in spas is correct. If you want to have 100 ppm CYA in a spa, then to kill the bacteria that causes "hot tub itch" you would need an FC level of at least 20 ppm FC and possibly more. The absence of bacteria, just like the absence of algae in a pool, does not mean that your pool or spa is sanitized or will prevent algae growth. It just means you were lucky or found no symptoms.

[Reese]

Thanks, Chem Geek! I'll take a look at this later. I'm sure I'll have more questions then! Have a good Sunday, and a Happy New Year!

Reese.