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Ph Lock What Is It?


marquismark
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Has anybody heard of this stuff? what is it? How it works? is it ok to use?

I have a problem with TA going to 50-70 and PH going above 7.8 in my bromine spa.

I have been told to keep TA at 100 -120 and PH of course 7.2-7.8. In a normal week I have been adding 3-4 oz. of sodium bicarbonate to get TA to 100 or above then 1-2 oz (or more of muriatic acid to get PH back in range. it seems like a lot of adjusting

Someone suggested this as a solution as I could then adjust TA as needed and it will lock the PH at the correct level. Then just shock as normal.

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If your pH tends to rise then you should NOT be raising the TA level. That is the problem and what you have been told is incorrect. When your TA got to around 50 ppm, did the pH not rise as quickly especially as it got to 7.8? If so, then you could just keep the TA at 50 ppm and you could add 50 ppm Borates (as with Proteam Gentle Spa) for additional pH buffering.

Is http://www.lesliespool.com/Home/Spas-and-Hot-Tubs/Spa-Chemicals/14125.html'>this product from Leslie's the pH Lock product you are talking about? I cannot find an MSDS for the product -- are there any ingredients lists that you can see? I'm guessing that it's a phosphate buffer. They do lock in pH, but can also create a precipitated mess or clogging of the filter if the water is hard since calcium phosphate will precipitate.

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Hi Chem Geek .

It is actually this product (I had the name wrong) http://www.spadepot.com/shop/Control-the-pH-P664C634.aspx. And here is the Active ingredient: phosphate buffer (as KH2PO4/K2HPO4). So your assumption was correct. I have been doing this weekly TA - PH adjustment for 5 years now and someone suggested this product. I always the adjustment based on values recommended by my dealer. In researching this product it led to this website.

I have read a bunch of the stickies and other posts. Wish I would have looked this up earlier I obviously have been over adjusting and will try your suggestion TA around 50 and add the borates, rather than the control the PH stuff.

Thank you for your help. But I am still curious how does phosphate buffer control the PH?

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Hi Chem Geek .

It is actually this product (I had the name wrong) http://www.spadepot.com/shop/Control-the-pH-P664C634.aspx. And here is the Active ingredient: phosphate buffer (as KH2PO4/K2HPO4). So your assumption was correct. I have been doing this weekly TA - PH adjustment for 5 years now and someone suggested this product. I always the adjustment based on values recommended by my dealer. In researching this product it led to this website.

I have read a bunch of the stickies and other posts. Wish I would have looked this up earlier I obviously have been over adjusting and will try your suggestion TA around 50 and add the borates, rather than the control the PH stuff.

Thank you for your help. But I am still curious how does phosphate buffer control the PH?

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Sorry I didn't see your post earlier. It got lost with all the spam hitting this site. Anyway, any weak acid or weak base can be used as a pH buffer. The pH buffering is strongest when the pH is closest to the pKa of the acid. See http://www.troublefreepool.com/ph-buffer-capacity-t31321.html'>this thread for the pH Buffer capacity at different pH for borates, CYA, carbonates and their combinations.

The main TA buffer system is that between bicarbonate and carbonic acid which has a pKa of 6.28 so gets stronger as the pH gets lower and is the main buffer that prevents a pH "crash" when using acidic sources of chlorine (especially Trichlor in pools). However, that buffer system has a side effect because it is in equilibrium with carbon dioxide which can outgas and such outgassing causes the pH to rise.

Cyanuric Acid (CYA) also buffers the pH, though that is not its primary role since it is mainly used to moderate chlorine's strength and to protect it from degradation from sunlight. The buffer system between cyanurate ion and cyanuric acid has a pKa of 6.83 so like the carbonates it gets stronger as the pH gets lower thereby helping to prevent a crash of pH when using acidic sources of chlorine.

The borate buffer system is that between borate ion and boric acid which has a pKa of 9.15 so unlike the others above, it gets stronger as the pH rises so helps slow down the rate of pH rise.

The carbonates and CYA systems described above actually have additional pH buffering points, but they are further away from normal pool/spa pH so I didn't describe them. The phosphate buffer system likewise has multiple points, but the one between the two phosphate chemicals you listed as ingredients is with a pKa of 7.21 so very close to the desired pH of pools and spas of around 7.5. By adjusting the ratio of the two phosphate chemicals, one can move the pH towards a desired amount and then it is buffered which with a lot of phosphate appears to be "locked in". As I wrote in my earlier post, the main problem with using a phosphate buffer is that calcium phosphate is relatively insoluble so when you add a phosphate buffer to water that has calcium in it, calcium phosphate precipitates causing a mess either on the floor of the spa or in the spa filter. This is a one-time problem until you change the water again. So use of a phosphate buffer with water that is high in CH is not recommended.

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I think this is related enough to post here since we are talking about "locking of Ph"....

Does anyone know how much of this gentle spa I have to add to my 420 gallon spa to get the required 50 borates? I don't know how to test for this and just followed the instructions for addition found on the bottle (can't recall the amount) at this time.

Thanks!

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50 ppm Borates in 420 gallons (from http://www.thepoolcalculator.com'>The Pool Calculator is 16 ounces (1 pound) weight or about 17 ounces (a little more than 2 cups) volume if it were boric acid. Proteam Gentle Spa is a mix of borate chemicals, but it's mostly boric acid. I bet their instructions were to get you to around 30 ppm.

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Proteam Gentle Spa is a mix of borate chemicals, but it's mostly boric acid.

I'm not sure if this is still true. I changed my water recently, and when I added Gentle Spa my pH spiked from 7.4 to over 8.0, and I had to add a sizeable amount of dry acid to get things back in line. Others have reported similar problems. I think that on my next water change I'll go with straight boric acid.

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It's still mostly boric acid, but apparently now has too much borax and it's the latter that makes the pH rise. It's definitely not just borax or else the pH would go up much more than over 8.0. And yes, you can just order boric acid directly which is cheaper to do anyway. It's available from The Chemistry Store, AAA Chemicals and DudaDiesel.

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  • 3 months later...

i have used this not too long ago as i kept going back and forth to the hot tub store with constantly needing chems due to ph swings he told me to try it .. i did and loved it it worked well but .... after about 2 mths started to have some water issues and wasnt sure if it was due to that or something else so i just drained my tub again here the other day and figured i would try it again

now we use our tub alot .. every day and the kids soak so a high load of people all the time .. maby that was also a issue not sure but if anyone has any suggestions on that i would appreciate some input

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You are probably running into problems with your high-use spa because you are not using enough oxidizer after each soak. By oxidizer I mean chlorine, bromine, or non-chlorine shock (MPS) depending on the system you are using. Every person-hour of soaking in a hot (104ºF) tub requires around 3-1/2 teaspoons of Dichlor or 5 fluid ounces of 6% bleach (or 3.6 fluid ounces of 8.25% bleach) or 7 teaspoons of non-chlorine shock (43% MPS) to oxidize bather waste if there is no ozonator. With an ozonator, the amounts may be half or less. These are just guidelines and your actual required use is whatever it takes to add after a soak such that you still measure at least a small residual (1-2 ppm FC or 2-4 ppm Total Bromine) just before your next soak. You can target a higher starting disinfectant level before the soak if you want more disinfection during your soak, though it will likely smell more.

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  • 4 months later...

I'm a newbie to the hot tub world and have enjoyed reading all that this forum has to offer (chem geek rocks). I've learned much (a dangerous thing). But this pH lock additive has got me stumped. Is it recommended or not? I used it at first, then got my test kit which indicated no calcium harness based on no color change to red. So I added a bit of calcium hardness and bang! a hot tub of milk. That the heck happened? I dumped the tub and wiped down the white film tub (calcium I think) and refilled. I tested the water and got the CH to 90 TA to 80 and pH to 7.4. I then added pH lock. Now the test kit acts like there's no hardness and the TA has jumped to 160. Now what happened? Not sure what to do? Water is now clear after filtering about 2 hours using full pumps.

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You should not try and raise the CH when using the pH Lock product or any phosphate buffer product. Calcium phosphate will precipitate if you add calcium to water that has a phosphate buffer in it. So if you've got a foaming problem and the reason you wanted to increase the CH was to reduce that, then you'd have to use a different approach to reduce foaming when you've got a phosphate buffer in your water.

Instead of using a phosphate buffer, why don't you do what we recommend (when using a hypochlorite source of chlorine as your disinfectant/oxidizer) which is to lower TA to 50 ppm and add 50 ppm Borates?

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Since I already have pH lock in the water, I think I'll follow your TA/Borates method after my next water dump (hopefully in 3-5 months). Going forward (with my current batch of water), my thought is to get the CYA back up to 20-30 (should only take a couple days) and simply add bleach as needed. Any foaming will have to be knocked down with a de-foaming additive.

Here's my observation......It appears monitoring TA and CH is futile with pH lock in the water. Both tests radically changed after adding pH lock. Thoughts?

What is your brutally honest thought of using pH lock?

After starting the TA/Borates routine, what is your recommendation to a user that needs to travel for 7-10 days and is unable to monitor his water?

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You are correct that with pH Lock you can't really control the CH since increasing it results in precipitating calcium phosphate. As for TA, that is also pointless since you will measure a high value for it but it won't be carbonates but will be the phosphate ions. I think that phosphate buffers to lock the pH in spas are one option, but as you point out it has side effects. For non-plaster spas, having the low CH isn't a problem so the main issue would be foaming. I think that the 50 ppm TA and 50 ppm Borates approach gives you more flexibility, but it doesn't lock in pH as strongly as a phosphate buffer.

As for travel, if you lower your spa temperature (i.e. 80-90 and not 104ºF) and keep the spa covered, then with the low TA and the borates the pH should remain fairly stable if you don't have aeration in your spa. Ozonators can aerate the water, but it's just something you'll have to see as for how high the pH goes. It is self-limiting (won't get much above 8.0 or 8.2) and with the low TA the risk for scaling is much lower even if you raise the CH to 120-150 ppm to avoid foaming.

I think the bigger issue with travel for 7-10 days is what to do about disinfection. You won't be there to add chlorine every day or two. If you are using bromine and have an ozonator then you can have a bromide bank so the ozonator will make bromine while you are gone. If you want to use chlorine, then you'd need some form of automatic dosing system such as a saltwater chlorine generator such as the ControlOMatic Technichlor.

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OK, thanks for you perspective on the pH Lock additive. It is handy for those that are not interested in water chemistry and want to keep it simple. But heavy use users will definitely have to deal with some foam.

I don't have an ozonator and do not use bromine so that's not part of the equation when traveling. With the pH Lock I now have in the water Ph shouldn't be a problem next month when we're away for 6 days. But disinfection, as you note, will be the challenge. Tossing in 5 lbs of salt and hanging a $290.00 generator wouldn't be my first choice. Any other tricks to try? Due to the loss of chlorine and the phosphate food the algae will enjoy due to the pH Lock additive I can just see returning from my trip to a green bath of algae.

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If your spa is covered then there won't be light for algae to grow. What is more likely is bacterial growth including biofilms. If you are away for just 6 days, then that's easy to handle. Just lower your spa water temperature and raise the chlorine level before you go. At 80ºF or cooler water temps, the chlorine loss should be low IF you didn't get behind in your dosing. If you raised the FC to 10 ppm, then even in a hot spa without an ozonator losing 25% per day the FC would be 1.8 ppm after 6 days. With the cooler water temp, the loss may be 15% or less per day so after 6 days would be 3.8 so should keep the water in good shape.

Usually, handling a trip of a week is not a problem. It's when it's much more than that such as 2 weeks or more that is an issue, though if you cool the water enough you can have the chlorine loss rate be quite low. An ozonator is a big problem as far as chlorine level for trips. The daily chlorine loss rate is typically 50% or more so after one week the chlorine level is only 0.8% of its initial value (so 10 ppm FC becomes less than 0.1 ppm). On the other hand, the excess ozone in the spa will kill off bacteria when the ozone is running, but it's not always on and the residual is small (though not that small, which is why it reacts with chlorine). Some people have reported returning to their spas with ozonators and no chlorine and found the water to be at least dull/cloudy and possibly have biofilms.

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Got another tidbit. Just did a little relaxing and was very surprised by what happened when I added Clorox bleach (unscented). Remember, I have pH Lock in the water. I had been using a off-brand bleach but read where Clorox was recommended because of its lower pH. So tonight I used it for the first time. After adding the correct amount, I was greeted by the foam monster. So much foam that the tub was over-run. Any idea what the heck just happened?

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Are you sure that the Clorox bleach wasn't "outdoor" or "splash-less"? Those have extra chemicals that can foam. You want to use regular unscented bleach (Clorox now has concentrated bleach at 8.25% that is fine to use so long as it is unscented, NOT splash-less and NOT "outdoor").

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  • 2 months later...

Great thread and impressive info getting shared here. Three points of interest for me:

1. bring me up to speed pls on using Clorox as the source of chlorine sanitizer. The spa store party line is don't ever do this. what are the essential points they are missing?

2. Ozone and Bromine spas on vacation: what is the decay rate and recommendation for 6+ days leave?

3. Buffers. I've used a phosphate buffer in my spa filled with cat ion exchange softened water. worked great, and foaming wasn't an issue for me, but its expensive, I did have to use anti-foam, and I found that the lock lasted for only 2 months or so. I'm starting to consider the borate method instead. Chem Geek you mentioned this is not as "strong" of a lock -- does that mean the pH fluctuations are wider and you still can't do anything about it, or that some amount of maintenance is still appropriate?

BTW I went to the proteam site and reviewed the Gentle Spa MSDS, as many others have done. the only ingredient they reveal is Sodium tetraborate pentahydrate (the rest is proprietary). The site does mention "pH neutral" and that "Fresh fragrance and moisturizers added" Hence if one is using an enzyme treatment such as the SpaGuard product, or a water freshener product which also contains these extra things, then the Gentle Spa doesn't seem like the best idea. In addition, with all the (older) threads discussing pH bounce with Gentle Spa I see Chem Geek's wisdom in recommending alternate sources for the Borates. thanks for that Chem Geek.

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You don't use ONLY bleach as the chlorine sanitizer. To do so would be far too harsh as the active chlorine level would be too strong. That's one of the reasons that spa stores say not to do it. You need to get Cyanuric Acid (CYA) into the water to moderate chlorine's strength. You can do that either by adding CYA directly or for spas most people just start out using Dichlor first and then switch to bleach after getting the CYA up to 30-40 ppm. This occurs after cumulatively adding 33-44 ppm FC of Dichlor. Then you just use bleach after that except you use Dichlor about once a month to make up for CYA that slowly breaks down from chlorine.

The other reason spa stores don't talk about using bleach is that you have to be careful in managing the pH of the spa and the pH will tend to rise too quickly unless you lower the TA significantly to around 50 ppm and also use an additional pH buffer of 50 ppm Borates. All of this is described in the sticky Dichlor/bleach Method In A Nutshell, but the TA should be lower than indicated in that sticky and the use of borates isn't really optional (unless you are VERY careful at monitoring the pH regularly).

An ozonator will make more bromine from a sodium bromide bank so if you have things tuned properly then you don't need to worry about any decay rate on vacation. That's one of the advantages of having an ozonator and using bromine. Bromine also lets you use bromine tabs in a feeder, though there is a limit to how long that will last without refilling.

The Borates not being as strong as the typical phosphate buffer used in spas means that you still have to monitor and adjust for pH, though if you have the TA be lower and you don't have too much aeration, and your pH target isn't too low, then the pH can rise more slowly. Some people have fairly stable pH while others have it slowly rise and a few still have it rise a lot (mostly due to lots of aeration).

If the Gentle Spa MSDS were accurate with regard to ONLY having sodium tetraborate pentahydrate, then you would have to add a LOT of acid when you used that product. There is no way they could claim it to be close to pH neutral unless they had either boric acid or some acid such as sodium bisulfate in it. If you started with a pH of 7.5, then adding 50 ppm borates using sodium tetraborate would result in a pH of 9.0. Since we don't see that happening, they must have some acid to compensate for the base or they have boric acid for most of the borate. I'm betting that they have mostly boric acid. Of course, you can get boric acid directly easily and at a lower price. Or you can buy 20 Mule Team Borax and add some of that and some acid alternating into the spa -- I think boric acid is a lot easier and is only slightly acidic (pH would go from 7.5 to 7.2).

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ok good I think I'm catching on here -- dichlor then switch to bleach manages the CYA and FC levels better, and at a lower cost but at the expense of some loss in pH control which can be moderated with the low TA+ Borates method? Boy that is not story you will hear in a spa store, to be sure!

ok also an aha moment I realize that ozone will oxidize the bromide reserve, assuming there is one. ok then I must not be tuned right as I am not getting that result: what I find is a pH rise from the start of the water lifecycle, so I begin with 50ppm TA, and a chlorine spa (at first) while using the brominating one-step granules. then as the water gets older, the bank builds, and pH tends to fall, I presume due to the lower pH of the bromine -- so TA gets raised into the 100ppm reagion. thats about where it is now. when I leave for a week I have to add soda ash to bump pH up to around 8 or higher, and I shock with MPS resulting in 15ppm or so bromine before I leave. when I get back, pH is around 7.6-7.8 but no bromine. where might I be going wrong?

regarding the "strength" of the buffer -- yes I've used the spaguard buffer and its strong allright. most of the time it produced pH on the high side for me. before I got used to it I tried to add some bisulfate to bring things down, and the spa just laughed at me, and I ended up destroying buffer, lol.

Basically what I'm hearing is that the borates method exerts control over pH swings but you still montitor things and manage pH and TA as you would normally do -- just not as often. I'm interested to try it for bromine -- anything specific to using Borates with Bromine that are critical?

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