Hot Tub Forum
Original => Hot Tub Forum => Topic started by: kervis on December 13, 2008, 11:19:58 pm
-
I suppose we all know that 7.2-7.8 is an acceptable range for pH, but then it gets inconsistent:
My spa log book says:
TA = Â Â Â Â 80-120
Calcium= Â 150-400
My owner's manual says:
TA= Â Â Â Â Â adjust to 125
Calcium= Â adjust to 150
pH= Â Â Â Â Â 7.4 to 7.6
When I bring my water in to the dealer to be tested, the printout says:
TA= Â Â Â Â Â 60-100ppm
Calcium= Â 200-400
pH+ Â Â Â Â Â 7.2--7.6
The directions on my Calcium hardness increaser bottle say:
Calcium should be 100-200ppm
I am thinking that the difference in some of those numbers could have me using more/less of certain chemicals than may be really necessary.
Any thoughts/comments/answers on this?
Thanks!
-
I wouldn't pay much attention to those ranges. Instead I would learn how the variables relate to each other, and how to keep your water balanced. The main problem in spas is rising pH due to aeration (air injection). The trick is to lower your TA enough to stop it, or at least reduce it greatly.
You can go here (http://www.poolspaforum.com/forum/index.php?s=0c5a25aaba483f99edec0d61098f2514&showtopic=13634) and learn about Water Balance. It will explain it in detail.
Let us know if you have any questions.
-
There is one place that I get my info from and that's the Taylor booklet that comes in the K-2005 kit (I'm sure it comes in other kits as well). I DO NOT trust dealer info as some dealers either may not know how to use their computerized testing machine or just want to sell you stuff. Remember any "computer" that gets calibrated can be calibrated wrong!
I have not had any problems following the Taylor book and have found a local pool dealer to not know what they were saying about certain water parameters.
It looks like your log book is following the Taylor book.
Then again if you have questions - you can ask here.
Hope this helps.
-
I agree with Vinny, the Taylor booklet has taught me a lot.
However, it may be difficult to keep your parameters in certain ranges if you don't understand the basics of Water Balance. For instance, don't expect your pH to stay bwrween 7.4-7.6 if your TA is 125 ppm. It just isn't going to happen in a hot tub with plenty of air jets. This is where beginners have problems (too high TA), and you're not going to find that info in the Taylor book.
I'll refer you again to my post Here (http://www.poolspaforum.com/forum/index.php?showtopic=13634) where I explain Water Balance. The key point is that your pH wants to rise in a hot tub with air jets. The best way to keep it from doing that is to lower your TA (60-80 ppm).
Also, there's a website called The Pool Calculator (http://www.thepoolcalculator.com/), that will let you plug in values and see where your overall (Satuation Index) balance is. It's an expanded version of the one that comes with the Taylor kit. It will also let you see how the different variables (CH, TA, pH) relate to each other to provide balanced water.
-
Nitro,
From what I learned the higher the TA (within reason) the more it locks in the PH which is why you need to use a lot of acid in order to lower PH with high alkalinity. A TA of 60 could produce PH swings where at 120 may not. I've never had to do this but I imagine that lowering your PH and alkalinity with acid and then bringing both in line will lock them in together.
I have said this many times - everybody's water reacts differently and in my water I have noticed my PH drifts down vs up. It also corresponds to the alkalinity reading and how quickly it dives ... the higher the alkalinity the slower it moves down. As a matter of fact I have found that using dichlor makes the PH slide down quicker than using bleach since apparently the end result of chlorine being used is an acidic reaction. I can go many weeks without my PH moving using bleach vs 3 weeks with dichlor.
Now to complicate matters with this I only use baking soda in my spa to raise both PH and alkalinity ... this doesn't work in my pool. There I raise the PH with Borax and then raise the alkalinity with baking soda and again it gets locked in for a while.
You are the first person I've heard to say lower alkalinity to combat PH going high - usually it is said to get the PH in line and lock it with the alkalinity. If PH creaps up usually the thing to do is get the PH to 7.2 and lock it in with the alkalinity, watch it, when it gets high hit the water with acid to get them down and start the process all over again.
-
I also find that keeping a lower TA prevents my pH from rising. Â My TA out of the tap is at about 80. Â My pH stays most stable if I keep TA at that level. Â Higher TA will pull my pH up.
-
Vinny,
You are correct that having a higher TA will prevent pH swings. However, it will only prevent swings from outside sources. i.e. the addition of Acid or Base. However, having a higher TA will cause the pH to rise more from aeration, i.e. the injection of air. In order to counter this pH creep, some kind of acid must be used i.e. Acid, Dichlor, or MPS. By lowering TA you will get larger swings from the addition of acid or base, but you you'll have less pH rise from aeration. However, if you don't add acid/base, or very little, it's a non-issue. Another way to reduce pH rise from aeration, is to add Borates (Borax) to the tub.
I agree that everybody's water acts different. However, I believe it depends on what is in the fill water to some degree, but what's put into the tub to a much larger degree. Not knowing everything you've put in your tub it's difficult to tell. But the main reason pH is lowered is the addition of something acidic, which could be Dichlor, MPS etc. However, using Bleach is relatively neutral, i.e. high pH while adding, acidic reaction when used up. So if only bleach is used the pH will have a tendancy to rise from aeration. Lowering TA and the use of a pH buffer (Borates) will reduce, if not stop it.
My tub has 60 ppm TA, 50 ppm Borates and my pH has stayed rock solid at 7.8 for the last month, since my last refill. After a refill, I add acid to lower my TA from 100 to 60 ppm, calcium to raise my CH from 100 to 200 ppm, Borates to raise it to 50 ppm and Dichlor to raise my CYA to 30 ppm. After that the only thing I add to my tub on a regular basis is bleach. Sometimes, I'll use MPS if I have high bather loads, but not on this fill. I rarely add acid, unless I'm lowering TA to fine tune it. And I never use Baking Soda, unless I mess up and add too much acid (only happened once).
Just out of curiousity, what level do you keep your TA at?
-
Actually I haven't measured TA for months (year?) only because I originally measured my PH and alkalinity out of the tap and both were low (PH - 6.8, alk below 80). They rise proportionatly together using baking soda and whenever I get to a good PH my TA is "within range". I have in the past used Borax in a pinch to rase the PH but found it didn't stay because my alkalinity was too low where as when I use baking soda it stays for weeks. I know Borax for raising PH ... Are you saying it adds different properties to the water vs soda ash?
In the past I have "balanced" my water within the Taylor specs but recently I have not been adding calcium. My tap water is also low in calcium and I used to bring it up to 150 to 200 PPM.
In the 3 1/2 years of owning my tub I have not had PH creep up but come down ... same as in my pool and I used bleach this summer except for a brief period where we went on vacation where I used trichlor.
I can measure it and tell you what it is. Unfortunately I can't do it for a couple of days as I negleted the tub and had to pour in a whole lot of bleach to kill the nasties. I'll let you know what it is in a few days.
-
Well, if you haven't been measuring TA, it's hard to tell where it is. I'd say if you have a problem with pH decreasing, your TA is on the low side, i.e. much less than 80. My point above was that if TA is on the high side, i.e. greater than 100, pH has a tendancy to rise via aeration. I'd be curious to know where yours is though. If you can measure and post it whenever get a chance that would be great.
Borates act as a pH buffer. i.e. they slow down the rate pH increases via aeration. Not to mention they give the water a nice silky feel to it. You add them by adding Borax to the tub. You also have to add acid to counter balance. Here (http://www.troublefreepool.com/so-you-want-to-add-borates-to-your-pool-why-and-how-t4921.html) is an excellent writeup about it.
-
OK, I was able to test my alkalinity
PH was 7.2 before adding all that bleach and its now at 7.4 and my alkalinity is at 80 PPM. I was planning on adding some baking soda to bring up the PH and alkalinity and give you a reading with that but since the PH is OK now I'm leaving it alone for now. As far as I remember bleach does nothing to raise the alkalinity
About the comment of "Well, if you haven't been measuring TA, it's hard to tell where it is." I have to disagree. Once you tested water parameters for a while and get a feel for what your water is doing then you don't need to test certain parameters too often. I found with my water that my PH and alkalinity rise and fall together and that when one is in an acceptable range, in this case I measure PH, then the other should be OK. I will say that at a PH of 7.8 my water's alkalinity is a bit on the high side and when I use dichlor exclusively alkalinity will fall and bring the PH down. But a lot of people either haven't tested their water enough or their water acts differently than mine. I believe that everyone should understand balancing their water but I think a lot skip this understanding.
Now about borates or borax - I didn't read the whole writeup but have been around the originator - pool solutions - for about 8 years. I guess the idea in the writeup is to use a lot of borax and "saturate" the water. The original concept was to use borax as a grocery store PH up and I do use it in my pool. As I said using baking soda in my spa brings up the PH as well where it has no effect to PH in my pool. I have read the using high levels of borates in the pool can act as an algecide along with proper water care procedures. I haven't had the need for algesides in my pool ... although last year I did have a problem with some type of alge eating my cya but that was taken care of by using large quantities of bleach for many days!
-
Vinny,
80 ppm TA is a lot lower than 120 ppm, which is technicaly still "in range". I can guarantee you if you raise your TA to 120, your pH will keep rising from aeration. In my earlier post I said, "The best way to keep it (TA) from doing that (creep) is to lower your TA (60-80 ppm).". My point was (and is), "Don't expect your pH to stay between 7.4-7.6 if your TA is 125 ppm.". And you will not find that information in the Taylor books.
When I said, "Well, if you haven't been measuring TA, it's hard to tell where it is.", I meant it's hard for ME to tell where YOURS is. I guess it was hard for you to tell too, because you had to measure it to know. ;) FYI, I rarely need to check my TA, because I know where it's at (60 ppm). The only thing I check regularly is FC, and sometimes pH.
I was under the impression your TA was higher (~120), because you seemed to disagree with my above post. Also, you said, "From what I learned the higher the TA (within reason) the more it locks in the PH which is why you need to use a lot of acid in order to lower PH with high alkalinity." That is true, but doesn't account for aeration. A TA above 100 will make it very difficult to keep pH < 8.0 in a hot tub with jets/air.
If you want to prove this fact for yourself, try this. Add Baking Soda to your tub to raise TA to 120, (about 3 oz). Measure your pH. Then kick the jets and air on for 30-60 mins. Then measure your pH again. Your pH will be much higher then before you turned on the jets. This is because aeration raises pH more with a higher TA. But I wouldn't recommend doing this until right before your next drain. Otherwise, you'll have to add acid to bring your TA/pH back down.
Lastly, Baking Soda has little effect on pH directly. Baking Soda raises TA, not pH. However, because your TA is higher, that causes your pH to rise from aeration. The reason why your pH doesn't rise in your pool from the addition of Baking Soda, is because your pool has a lot less aeration than your hot tub. Therefore, a higher TA in a pool won't effect pH as much as it does in a hot tub.
-
Like Vinny, my PH keeps getting lower as time goes on. Â After a fresh fill, I have a hard time keeping the PH down. Â After the water starts to get "old" I have a hard time keeping the pH up.
-
Like Vinny, my PH keeps getting lower as time goes on. Â After a fresh fill, I have a hard time keeping the PH down. Â After the water starts to get "old" I have a hard time keeping the pH up.
I have a similar problem but nothing to do with my PH... ;)
-
:o
-
Like Vinny, my PH keeps getting lower as time goes on. Â After a fresh fill, I have a hard time keeping the PH down. Â After the water starts to get "old" I have a hard time keeping the pH up.
If you have a problem keeping pH up, you may want to raise your TA with Baking Soda. Where is your TA at now?
Also, Dichlor is acidic and will lower TA/pH over time. If you don't raise your TA periodicly, it will get too low.
-
I have a similar problem but nothing to do with my PH... ;)
That's about the funniest thing I heard all week. ;D
-
Never thought too much about aeration before. I just tested my water from the tap with my Taylor test kit--haven't done this in years. Here are my results: PH = 8.0+, Alk = 100, Cal = 90
Normally I throw in a little dry acid with a new fill and the PH usually drifts down on it's own after a couple weeks. My calcium has always been low for some reason. When the tub was new I used to add calcium increaser but I don't hassle with it anymore. Any huge concerns if my calcium is always under 100?
-
If you have a problem keeping pH up, you may want to raise your TA with Baking Soda. Where is your TA at now?
Also, Dichlor is acidic and will lower TA/pH over time. If you don't raise your TA periodicly, it will get too low.
I haven't tested TA. I'll keep the Baking Soda idea in mind.
-
When I have a fresh fill and test my water both PH and alkalinity are low. I didn't test my alkalinity out of the tap recently but the PH is below 7.0. This is without aeration or dichlor or anything else - just plain water. I don't add anything but baking soda and my PH along with alkalinity goes up - this is done with all pumps on and no air for about 20 minutes and I check the PH hours later and add more baking soda if needed. My PH stays there for weeks and then starts to go down, when it gets to 7.2 or so I add more baking soda and my Ph goes back up.
I don't doubt what you say about aeration but my PH has never went up - always down. I do understand that the overall effect of dichlor is an acid result and this along with using MPS that has a PH of about 4 will bring down the PH in the water. I attribute my PH recently going up from 7.2 to 7.4 due to the amount of bleach that I put in (PH of about 13) and the fact my alkalinity is at 80 and not 120. I attribute it to the bleach ONLY because I added so much to the tub that the bleach that wasn't used up through any type of reaction (sanitizing or oxidizing) was disipated due to the heat and the overall effect was for the PH to go higher. I never have the tub running with air since I don't want to inject cold air into the hot water when I am not using it - air wasn't a factor this time of the PH rise.
By all logic I agree that my PH should not be affected too much by adding baking soda but it does. After the initial 20 minutes of mixing I have a circ pump and my tub only runs the main pumps for 1 or 2 minutes a day without air. In the past I have had a PH of 7.8 and an alkalinity of over 120 and my PH still creaped down, it just took a little longer to get there. I will say that I don't use my tub that often and when IÂ use the correct amount of bleach my PH stayed rock steady for a long time.
To the point of not knowing where the alkalinity is - no I didn't know exactly where it was but at a PH 7.2 I knew it was about "in range", which it was. I guess you test your water all the time ... I've gotten past that point only because my water behaved the same way pretty much all the time I tested it. At 7.2 I dump in some more baking soda and both my PH and alkalinty go higher. I could test my PH and alkalinity once I add it but I only test the PH hours later to see if it has come up to where I want it. If it goes higher because of aeration - Â couldn't tell you but it stays there for weeks using dichlor or months using bleach. I've come to the realization that "worrying" over the water vs understanding what MY water is doing was just a waste of my time. I agree 100% that everyone who has a pool or spa should understand water chemistry and I do understand that balanced water is the ideal solution but even balanced water has a range in which everything is OK. There are no finite numbers to balance water - once I understood this concept I started not nitpicking.
Personally, I am more concerned about the sanitation aspect of the pool and spa vs if they are at 7.2 or 7.8 PH - both are in range. Also, for me a alkalinity of 80 is no big deal vs 120 IF the PH falls into place. I asked questions of chemgeek months ago about bleach and he answered my questions to my satisfaction and now I use it.
Vinny,
80 ppm TA is a lot lower than 120 ppm, which is technicaly still "in range". I can guarantee you if you raise your TA to 120, your pH will keep rising from aeration. In my earlier post I said, "The best way to keep it (TA) from doing that (creep) is to lower your TA (60-80 ppm).". My point was (and is), "Don't expect your pH to stay between 7.4-7.6 if your TA is 125 ppm.". And you will not find that information in the Taylor books.
When I said, "Well, if you haven't been measuring TA, it's hard to tell where it is.", I meant it's hard for ME to tell where YOURS is. I guess it was hard for you to tell too, because you had to measure it to know. ;) FYI, I rarely need to check my TA, because I know where it's at (60 ppm). The only thing I check regularly is FC, and sometimes pH.
I was under the impression your TA was higher (~120), because you seemed to disagree with my above post. Also, you said, "From what I learned the higher the TA (within reason) the more it locks in the PH which is why you need to use a lot of acid in order to lower PH with high alkalinity." That is true, but doesn't account for aeration. A TA above 100 will make it very difficult to keep pH < 8.0 in a hot tub with jets/air.
If you want to prove this fact for yourself, try this. Add Baking Soda to your tub to raise TA to 120, (about 3 oz). Measure your pH. Then kick the jets and air on for 30-60 mins. Then measure your pH again. Your pH will be much higher then before you turned on the jets. This is because aeration raises pH more with a higher TA. But I wouldn't recommend doing this until right before your next drain. Otherwise, you'll have to add acid to bring your TA/pH back down.
Lastly, Baking Soda has little effect on pH directly. Baking Soda raises TA, not pH. However, because your TA is higher, that causes your pH to rise from aeration. The reason why your pH doesn't rise in your pool from the addition of Baking Soda, is because your pool has a lot less aeration than your hot tub. Therefore, a higher TA in a pool won't effect pH as much as it does in a hot tub.
-
Vinny,
You should do whatever works for you. I was just pointing out to the OP that having a TA of 120 ppm, while still in range, could cause pH creep issues from aeration. If my my TA is even 100 ppm, my pH creeps up too much. I found that with my TA at 60 ppm, my pH is rock solid at 7.8, and I don't need to add any Acid or Baking Soda after the initial dose.
Also, I don't test TA all the time. I only test it when I fill the tub and adjust it, which was over a month ago. I just keep an eye on pH to make sure it stays at 7.8. If my pH does drift, I adjust TA, not pH. If your TA is well tuned, your pH will be stable.
I agree, Sanitization is very important, but the OP was referring to Water Balance in this thread. BTW, I also learned to use Bleach from ChemGeek. He is the expert on that method, and Water Chemistry in general.
-
Never thought too much about aeration before. I just tested my water from the tap with my Taylor test kit--haven't done this in years. Here are my results: PH = 8.0+, Alk = 100, Cal = 90
A lot of people don't know about aeration causing a rise in pH. I only know it because I learned it on another board. It can cause a lot of issues if you're using bleach to sanitize your tub. If you use Dichlor it's not as apparent, because Dichlor is acidic, and lowers TA/pH over time anyway. However, bleach is relatively pH netural, so it becomes more apparent.
Normally I throw in a little dry acid with a new fill and the PH usually drifts down on it's own after a couple weeks. My calcium has always been low for some reason. When the tub was new I used to add calcium increaser but I don't hassle with it anymore. Any huge concerns if my calcium is always under 100?
Unless your Calcium is really low <50 and/or you also have a low pH (<7.2), I wouldn't worry about it. If you keep your pH in the 7.4-7.8 range you're fine.
-
Di chlor is close to netural at 6.8 and bleach (sodium hypochlorite) has a very high PH of 13 so its all ready an issue. Where are you getting that bleach is PH netural?
-
The reaction of chlorine when its doing its job is an acidic reaction. If you add enough dichlor to do the job (3 PPM) and enough bleach to do the job (3 PPM) the overall effect for dichlor is to become acidic where the bleach becomes PH neutral.
Initially what you said is true but after the reaction things change.
-
What Vinny said is correct.
-
Just a follow up on the PH vs alkalinity and using baking soda.
I added 2 oz of baking soda to my tub Friday night and the PH went to 7.8 and alkalinity went to 110, originally the PH was 7.4 and the alkalinity was 80. I measured these today.
Other than jets without air running to mix the baking soda in the water and some dichlor to sanitize the water nothing else has been added.
-
Vinny,
FYI, pH rise doesn't necessarily require physical aeration. Just having the water exposed to air can still allow outgassing, though not as much as injecting air. The pH would rise to 7.8 if only 5.4% of the carbonate in the water were outgassed. Two days could have be enough time for that to happen.
2 oz of Baking Soda would raise your pH from 7.4 to 7.5, with no outgassing (assuming 350 Gal tub). So the rise from 7.5 to 7.8 was from outgassing.
-
But it doesn't affect pool water and why?
It would seem that whatever a tub's water does would be what a pool's water does. I understand the volume difference but you would be adding the same proportionate amount of baking soda, chlorine or whatever to a pool as you would to a spa.
I just doesn't make sense to me that a spa's water is that much different than a pool. I can see if air is injected but other than a little splashing from the neck jets there is no air injected.
Also I don't have any covers on the pool during the summer and it has all the time to out gas. For some reason I have a hard time believing that spa water behaves that much differently than pool water with PH & alkalinity and it has to do with simple out gassing.
Can you explain why 400 gallons is affected by 2oz and 13,000 gallons is not when I raise the alkalinity from 80 to 110 or 120 in the pool. I would imagine I would be using approx 32 times more baking soda (13000/400 = 32.5) which would equal 64 oz.
-
Can you explain why 400 gallons is affected by 2oz and 13,000 gallons is not when I raise the alkalinity from 80 to 110 or 120 in the pool. I would imagine I would be using approx 32 times more baking soda (13000/400 = 32.5) which would equal 64 oz.
Temperature!
The water temp is the key. The rate of outgassing is also a function of temperature, with faster outgassing at higher temperatures.
If you want to see the isolated effect of adding baking soda to your hot tub, you should measure the pH after 15-30 minutes. There is no reason to wait a day or two. Acid and Base are well dispersed within 30 mins with the jets running.
I balanced my friend's hot tub water in a few hours, when his TA was over 400 ppm, and his pH was too high to measure. If you understand the point about pH rise via aeration, you can balance your water in a day, and never (or very rarely) need to add acid or base.
-
Temperature!
The water temp is the key. The rate of outgassing is also a function of temperature, with faster outgassing at higher temperatures.
If you want to see the isolated effect of adding baking soda to your hot tub, you should measure the pH after 15-30 minutes. There is no reason to wait a day or two. Acid and Base are well dispersed within 30 mins with the jets running.
I balanced my friend's hot tub water in a few hours, when his TA was over 400 ppm, and his pH was too high to measure. If you understand the point about pH rise via aeration, you can balance your water in a day, and never (or very rarely) need to add acid or base.
The general rule of thumb here is to wait at least 4 hours (longer the better) to keep from measuring PH that is swinging vs steady PH. I will test the PH in 20 minutes next time to see if PH is lower. Besides it was raining and I didn't want to get wet! ;D
I thought you were going to say that temperature affects outgassing so does the effect on the cabonate in the water change over time? Such as a higher change will occur in the first 3 days vs (1,2,3, ...) week(s) later of adding baking soda if the temp rises higher.
-
I thought you were going to say that temperature affects outgassing so does the effect on the cabonate in the water change over time? Such as a higher change will occur in the first 3 days vs (1,2,3, ...) week(s) later of adding baking soda if the temp rises higher.
The higher the pH the slower the outgassing (pH rise). Eventually it will hit an equilibrium that's dependent on your TA. This is why you should adjust TA, not pH. Your pH will fall in line if your TA is tuned. However, if you ignore TA and focus on pH, it's more difficult to keep your pH under control, without constantly adding acid or base. The only reason to add Acid or Baking Soda, should be to fine tune your TA to make your pH more stable.
Merry Christmas!
-
Since I don't have a problem with TA and PH as they rise and fall together I can't comment on what you've said. Your method does work for me and as I said I "know" my alkalinity is in line with my PH based on my water testing and watching the TA and PH rise and fall, when I add baking soda I see my PH rise if this the result of out gasing as you suggest - great; I know that adding baking soda will make my TA rise.
The ONLY problems that I have with your method and this might come from my ignorance is that your method doesn't necessarily work for everybody. I've seen posts where people have high TA and low PH - if they drop the TA by using acid then PH will drop as well. And my pool water has been at 95º, a high TA but the PH stayed the same.
I stopped posting/viewing poolsolutions a few years ago. I do pop in from time to time but a lot of what is being said now on other websites came from that website. Maybe the info out of it has evolved through the years and I remained stagnant in my knowledge, chemgeek wasn't around that website when I was active there. I don't doubt what you say but it doesn't seem to jive with what used to be said on the poolsolutions website or what professionals say. Maybe spa water is different than pool water and it does seem to act differently at times for me.
I guess it might be time for more internet water chemistry classes! :D
-
The ONLY problems that I have with your method and this might come from my ignorance is that your method doesn't necessarily work for everybody. I've seen posts where people have high TA and low PH - if they drop the TA by using acid then PH will drop as well. And my pool water has been at 95º, a high TA but the PH stayed the same.
The only reason why pH would remain low (<7.4) despite TA being high (>100), is if there is little aeration. ie. in a pool, or hot tub with few air/jets. However, anyone with many jets/air in their hot tub will experience pH rise, if TA is high.
I stopped posting/viewing poolsolutions a few years ago. I do pop in from time to time but a lot of what is being said now on other websites came from that website. Maybe the info out of it has evolved through the years and I remained stagnant in my knowledge, chemgeek wasn't around that website when I was active there. I don't doubt what you say but it doesn't seem to jive with what used to be said on the poolsolutions website or what professionals say. Maybe spa water is different than pool water and it does seem to act differently at times for me.
I'm not sure which site was around first, but I learned most of this stuff from PoolAndSpaForum and TroubleFreePool. Chem Geek (the expert) posts on these forums regularly, and has taught me a lot. Waterbear is another expert who I learned a lot from.
I guess it might be time for more internet water chemistry classes! :D
Check out this (http://www.poolspaforum.com/forum/index.php?s=6cb292c7fcae894b497962cb92fa9531&showtopic=13634) post where I documented the latest knowledge in Water Balance and Sanitation using the Dichlor/Bleach method. I just compiled this info from other sources and posted it in one place.
-
Alright. I'm fairly certain I understand, to some degree atleast, everything being discussed in this thread. The whole aeration thing is a bit new but I think I get the jist of it. The only thing is that my water apparently doesn't follow some of the characteristics of a hot tub being exposed to a high amount of aeration as some are stating...maybe I just overlooked something. Anyways, here's a little info on my water-
* all tests are done with the Taylor k-2005.
-out the tap  pH 8.0, Alk 100-110, CH 150-180. No signifacnt change once my spa is filled and heated with the source water.
-Through the past two years I've learned not to adjust anything, as the alk and pH ALWAYS fall together. I seriously only add dichlor for atleast a month after a refill. I test my pH every week. When she finally drops below 7.2, I test Alk as well(it's typically < 80 by then) and adjust them accordingly with Sodium BiCarbonate. I do this maybe 2-3 times a fill(typically 4 months) and that's it.
-I soak almost everyday and I ALWAYS have the air injectors on when I do. What's got me confused is that according to the 'aeration effect' and my intial readings out the tap, my pH and Alk should be climbing not falling, right??
-
I seriously only add dichlor for atleast a month after a refill.
The consumption of chlorine is acidic so even though Dichlor is initially nearly pH neutral upon addition, when the chlorine gets used up this is the same as if you added acid to the water. Â In 350 gallons, the addition AND subsequent consumption of 4 ppm FC from Dichlor is identical to 1.2 teaspoons of dry acid in terms of the effect on pH if there were no outgassing.
If you wanted your pH to be more stable in your situation using Dichlor, you could have the TA be even higher. Â The pH rise from outgassing would then balance the pH drop from the Dichlor addition and consumption. Â Over time, the TA would drop and you'd need to add more, but by then some of the TA measurement will be CYA (about 1/3rd, at pH 7.5) built up from the Dichlor and the CYA does not outgas. Â However, you already have fairly high CH so you wouldn't want the TA to get much above 110 ppm anyway in order to prevent scaling.
Richard
-
Chad,
As Chem Geek mentioned, adding Dichlor is the same as adding acid. This will lower your TA and pH over time, therefore counteracting pH rise due to aeration.
Vinny (I assume from a prior post) and I switch to bleach after a week or so of using Dichlor. Bleach has a relatively netural effect on TA/pH, so pH rise from aeration is more apparent. If you only use Dichlor, you can try raising your TA higher, which will prolong your pH from dropping.
-
The consumption of chlorine is acidic so even though Dichlor is initially nearly pH neutral upon addition, when the chlorine gets used up this is the same as if you added acid to the water. [glow] In 350 gallons, the addition AND subsequent consumption of 4 ppm FC from Dichlor is identical to 1.2 teaspoons of dry acid in terms of the effect on pH if there were no outgassing.[/glow]
If you wanted your pH to be more stable in your situation using Dichlor, you could have the TA be even higher. Â The pH rise from outgassing would then balance the pH drop from the Dichlor addition and consumption. Â Over time, the TA would drop and you'd need to add more, but by then some of the TA measurement will be CYA (about 1/3rd, at pH 7.5) built up from the Dichlor and the CYA does not outgas. Â However, you already have fairly high CH so you wouldn't want the TA to get much above 110 ppm anyway in order to prevent scaling.
Richard
Thanks Richard. I especially apreciate the highlighted statement...very useful information!
-
Probably even better is to say that [glow]the addition and consumption of 2 teaspoons of Dichlor is identical to 1.2 teaspoons of dry acid in terms of the effect on pH if there were no outgassing[/glow].
The above statement is independent of spa volume. Â I should note that "outgassing" refers not only to carbon dioxide outgassing that raises the pH when there is higher TA, lower pH and/or more aeration, but also refers to chlorine outgassing. Â The latter doesn't happen very much. Â You can partly see this from typical FC usage when there is no spa use (some chlorine use also comes from a slow oxidation of CYA by chlorine). Â Any chlorine that outgasses and doesn't get consumed in the water will not be acidic so the net result would be more of a pH rise (or less of a pH drop).