DonR6702

Richard, you can in fact strip dissolved carbon dioxide from water with aeration, as you can strip almost any dissolved gas from water. It is done all the time in industry. Carbon dioxide is different from some gases in that it reacts with water, forming an equilibrium between carbon dioxide and carbonic acid, but the stripping of carbon dioxide from water is not dependent on that equilibrium. It does, in fact, disrupt that equilibrium, which is quite weak at normal spa pH values. The great majority of carbon dioxide in water exists as the dissolved gas at pH 7.5. Stripping of gases via aeration is a purely mechanical process, so it can't be described by equilibrium equations. With vigorous enough aeration for a long enough time you can strip out practically all of the carbon dioxide, including that which is in the carbonic acid form - in this case, the equilibrium actually aids the stripping process because as carbon dioxide gas is purged from the water, carbonic acid dissociates to produce more carbon dioxide, which is subsequently stripped from the water. This is why the pH goes up when you aerate water. With moderately alkaline water having moderately high calcium hardness, it is possible to raise the pH high enough, with aeration only, to precipitate calcium carbonate. Your statement: is quite confusing. I guess it indicates that your experience is limited to pool and spa water starting from water with relatively low alkalinity. Water chemistry is much more complex than that. I just refilled my spa, and the tap water had pH 8.0 with 35 ppm alkalinity. This pH is higher than normal for my location, but the alkalinity is right in line. My tap water normally runs from pH 6.8 to 7.5, with alkalinity between 30 and 40. I have been testing and logging my tap water chemistry for years (for aquaria use as well as for my spa), and the alkalinity has never been below 30, while the average pH is about 7.2. There are some parts of the US where tap water alkalinity runs to 150 ppm or higher. There is no "normal" value of alkalinity in water, and your term "over-carbonated" is misleading. The carbonate species in spa water are in equilibrium by definition except when steps have recently been taken to make adjustments. In some parts of the US it is necessary to lower the alkalinity of tap water after adding it to a pool or spa. This water, even if the natural alkalinity approaches 200 ppm, is not "over carbonated" or "over-saturated" with carbon dioxide. It is in fact in equilibrium, and the amount of dissolved carbon dioxide is very low compared to the bicarbonate and carbonate species. If the spa water was "over-saturated" with carbon dioxide, you wouldn't need to aerate in order to purge the carbon dioxide, it would happen naturally. After you strip carbon dioxide, or any other gas present in the atmosphere, from water by vigorous aeration, those gases diffuses back into the water and dissolve according to Henry's Law and Graham's Law. In most cases this is a slow process, though it's faster for carbon dioxide than for many other gases (19 times faster than oxygen, for example). Carbon dioxide continues to diffuse into the water from the atmosphere and to dissolve until equilibrium is reached, and the pH drops. If you don't believe it, don't take my word for it, try it. Measure your spa's pH, then aerate vigorously for an hour or so. Measure the pH - it will have risen, of course. Then let the spa sit, with no chemical additions and normal water circulation without air injection for 24 hours or so. The pH will have fallen back towards the first value. How could it be any other way, when the alkalinity and temperature remain unchanged?

Good analysis, Richard. I would add one thing to it which you mentioned in one of its contexts but failed to mention in the other context - the equilibrium between dissolved carbon dioxide and carbon dioxide in the air. You mentioned that outgassing of carbon dioxide to the air is slow, which it is. But you didn't mention that dissolution of carbon dioxide from the air is also quite slow, and it is this dissolution that re-establishes the equilibrium after carbon dioxide has been stripped from the water with vigorous aeration. When you add acid to the spa, it reacts with bicarbonates (there are practically no carbonate species in aqueous solution below pH 8.5) to produce the salt of the acid used plus carbonic acid, as you noted. The alkalinity drops and the pH drops, and a new equilibrium between carbon dioxide, carbonic acid and bicarbonate is established quickly. By the time the added acid is mixed thoroughly with the water that reaction is finished. But the new, lower pH means that carbon dioxide is less soluble, so some of it escapes to the atmosphere via that slower mechanism you mentioned. Though slower than the initial reactions, that mechanism too will be complete within minutes, and will be accelerated by mixing and/or aeration. But what happens now if you turn on the pumps at high speed with air injection? Carbon dioxide is stripped from the water fairly quickly. The carbonic acid --> carbon dioxide equilibrium is pushed to the right with carbonic acid decomposing to produce more carbon dioxide, which is stripped from the water, etc., etc., and the pH rises. It is possible with vigorous aeration at pH in the mid 7's to drive most of the carbon dioxide and carbonic acid out of the water. But in this process the alkalinity remains unchanged, so the equilibrium is disrupted. After the vigorous aeration ceases, the equilibrium is re-established by the reaction of atmospheric carbon dioxide with water at the water surface. This reaction is relatively slow, depending on the water temperature and pH, and the ratio of water volume to surface area. It could easily take more than an hour for the pH to return to its new (lower) equilibrium value. In short, vigorous aeration will always raise the pH, but it doesn't change the alkalinity, so the pH will gradually return to its equilibrium value. Don

You shouldn't be checking the pH during or shortly after aerating. Aerating disturbs the equilibrium between carbonic acid, bicarbonate and bicarbonate, and the pH will go up, but when aeration ceases, the equilibrium will gradually be re-established. You should run the pumps for a few minutes after adding acid, but leave the air injection off. When you add acid (assuming you're adding enough to make a difference) you permanently destroy some of the alkalinity, and the pH **WILL** go down. The equilibrium shifts away from carbonate (high pH) towards bicarbonate (moderate pH) and carbonic acid/carbon dioxide (low pH). Aerating will always raise the pH temporarily, but the new balance will take effect after aeration ceases for a while. When I add acid to my spa, I don't aerate, but just run the pumps for a few minutes. The pH always goes down, and stays down unless I check it during or shortly after aerating. It is, after all, the equilibrium pH that you are interested in, since most of the time (I'm assuming here) you are not aerating your spa. It is that equilibrium pH that determines the effect that your water has on bathers and on the equipment. Try checking it first thing in the morning, and don't aerate after adding chemicals to adjust the pH. The carbon dioxide fluctuations that can cause rapid temporary pH changes can mislead you.

I would advise storing strips and kits at room temperature. Taylor has a generic recommendation for all of their strips and kits that they be stored at 36 to 85 degrees Fahrenheit. Both my LaMotte and BioGuard test strips specify on the bottle that they be stored at room temperature.

I don't use bromine, but I will try to answer. If you're adding bromide salts once a month or so to maintain a bromide bank, the MPS you add will be used up converting the bromide to bromine, as long as there is sufficient bromide reserve. So in that case it's important to maintain that bromide reserve. Unfortunately there's not a test kit available for bromide, so you have to follow the manufacturer's recommendations for how often to add bromide and how much to add. If you start seeing the bromine level fail to rise after adding MPS, your bromide level is probably low or depleted entirely. If you're using bromine tablets and just adding the MPS as a shock, try to keep the bromine dispenser full so (hopefully) the bromine level never drops below about 3 ppm, and only add MPS when indicated by water quality issues, when the bromine level can't keep up with the load, or when your experience tells you there's about to be a problem due to usage. I got into trouble by getting into a routine of adding MPS on a regular schedule when it wasn't really needed. Anyone else out there who uses bromine and MPS, feel free to correct or add to this. Don

Are you using MPS (non-chlorine) shock to activate your bromine? I had this problem with the K-2006 Chlorine FAS-DPD test. The conclusion reached by Taylor tech support was that the interference came from MPS (non-chlorine shock). It is well known in the analytical chemistry world that MPS reacts with ferrous ammonium sulfate (FAS, the titrant in the Taylor K-2006 and K-2106 kits), so if you perform the test while there is still significant active MPS in the spa the results will be high, whether you are analyzing free chlorine or bromine. The conventional wisdom is that if you wait "a few hours" after adding MPS, the interference will be gone, as the active component of MPS decomposes and no longer reacts with FAS. But the question is "How many hours are a few?". The answer is, it depends on the overall water chemistry, the water's oxygen demand, and the level of MPS added. Twelve hours after last adding MPS to my spa, I saw interference causing the free chlorine to read about 9.5 ppm too high. The interference diminished slowly over the course of a few days, but it was still present to the extent of about 1 ppm (high chlorine reading) after 10 days. It's still unclear to me why this interference persisted for so long - the Taylor tech support rep was reluctant to blame the reagents in my kit, and I concurred with that since I analyzed chlorine standards made with bleach and bottled water and those analyses worked fine. I can say that my spa water was about 3-1/2 months old and the spa had been used relatively heavily (for my situation at least, perhaps lightly for some of you), so I was preparing to change the water anyway. I understand that with bromine sanitation you may be adding MPS frequently to activate the bromine. In this case, I think it's important to determine just how much is needed to do the job and avoid adding large excesses. In my case, my spa began leaking around a fitting just before I was going to change the water, so it's now empty and awaiting a service rep. When I fill it again, I will either stop using MPS or at least use it much more sparingly. Don

No, it shouldn't make the TA reading unreliable - but it does lower TA as well as pH. Alkalinity and pH go hand-in-hand. Anything that lowers the pH will lower the alkalinity too, and vice versa. There's no need to wait around for things to correct themselves because they probably won't. If you're using non-buffered MPS, add TA increaser (sodium bicarbonate, or baking soda) to get the alkalinity back up, and your pH will come up to. I use non-buffered MPS and practically never need to add anything to raise the pH, only the alkalinity.

I use them occasionally because the odor of chlorine bothers my wife (personally, I like the odor of chlorine in low concentrations). I haven't noticed any problems due to the use of liquid spa fragrances except a slight increase in chlorine demand. The brand I use lists the ingredients on the bottle, and all ingredients are relatively innocuous organic liquids. Some of the liquid fragrance labels I have looked at claim that the products inside make the water "silky" or "smooth", or some other similar adjective. Those labels imply that the products contain oils, surfactants, softenes or some combination of these. I steer away from those products. Some of the crystalline spa fragrances, on the other hand, contain mineral salts like magnesium sulfate (epsom salt), which will increase the total dissolved solids, and in the case of magnesium salts, they will increase the hardness too. Depending on the hardness test method you use, magnesium may not show up as total hardness. It does show up as total hardness with the EDTA titration test employed in some of the Taylor kits. Hardness due to magnesium does not tend to form waterline deposits easily since magnesium carbonate is significantly more soluble in water than calcium carbonate, but the contribution of magnesium to buldup of scale around your heater will be quite significant at high concentrations. Don

Thanks for the help, no ingredients on the "Ultra-Spa" bottle, but I did find this in a post from Tom at Arctic Spas...."I received the MSDS from our supplier. Ultra-Spa is a proprietary blend of borates used as a spa water conditioner and buffer." The bottle says to use 6 capfuls at re-fill, then 2 caps per week. Our delivery guy told us "you can't use too much of this stuff". So, since it smells really good, we'd throw in a cap or two every couple of days or so for the first week or two..been using it much less since then though. So, from what I'm guessing, we should use this stuff a little more sparingly now that the water is clear from the clarifier, and also lower pH slightly as well and see it that helps. Without knowing exactly what's in it, it's impossible to recommend how much to use. Personally, if the manufacturer isn't willing to tell me what's in their product I'm not willing to put it in my spa. The use of borax, which is sodium borate, as a pH buffer in a spa is well documented, and there are products containing borax whose compositions are well known. The laundry aid "20 Mule Team Borax" for example is 99.5% sodium borate decahydrate. When added to a spa, it is necessary to add acid along with it to keep the pH in check, as borax forms an alkaline solution in water. Without the acid, borax is not a buffer, it is a base. Since your water apparently reached the calcium carbonate saturation point, I recommend draining a significant part of it if not all of it. Lowering the pH will help, but you will likely get back to that saturation point before long unless you replace a significant portion of the water. And again, if I were you, I wouldn't be using that product without knowing what's in it. If it's the fragrance you like, you can buy fragrances whose compositions are known (at least the list of components in order of relative concentration). I would recommend trying some of the liquid fragrances made specifically for spas, as they should have minimal effect on the water chemistry, unlike some of the crystalline fragrance products, which increase the hardness and TDS, pushing the water towards that dreaded saturation point. Regarding the filter, the MicroPure is a "depth filter", meaning that it excludes particles by virtue of not only its porosity but its thickness. The porosity is larger than the rated retention (1 micron in the case of the MicroPure), but particles of the rated size are unlikely to make their way all the way through the thick filter medium. Depth filters can actually increase in efficiency as trapped particles accumulate, and can handle heavy particle loads until one of two things happens - either the filter becomes clogged or the trapped particles begin to break through. In either case you have a "filter" that's worse than no filter at all. Since conventional pleated filters are completely satisfactory for normal spa use and can be cleaned and reused, the use of depth filters like the MicroPure is not justified IMHO. In any case, I think it's time to change your filter after cleaning up the preciptitate problem. Good luck, Don

We are on all Arctic Pure brand chemicals right now that came with the startup kit: bromine with floater set on 2 or 3, with ozone. Bromine levels are generally between 3-5ppm. We use a full capful of Arctic Pure Refresh MPS shock after every use, which is every one or two night or so. Also have a "Zorbie", if that helps at all. pH is generally around 7.5-7.8, TA around 80-100, total hardness is bang on according to test strips. No buildup on shell surface or anything like that. I even gave it a good super shock of 4 capfuls of Refresh a couple of days ago to see if that would help, it did nothing. When you look close at the water, it looks like billions of little white particles floating around...from a distance, just looks hazy. From what I've read, we are using more than enough sanitizer...most people on ozone use 0.5-1 ppm bromine and don't shock all the time. We are at 3-5ppm and always shock. How could this be microbial? Anyway...cloudiness was not always there...water was clear for 2 weeks until we started to notice it gradually get cloudier. The cloudiness is all the time, then gets worse when the jets are on. Goes back to the original cloudiness after a couple of minutes...I guess some of this might be from air bubbles. Anyway, now after the Arctic Pure Easy Clear clarifier, the water is perfect again. Fyi, we also use Arctic Pure Ultra-Spa conditioner, as recommended by the dealer...it is supposed to "condition and clarify the water" and "maximize effectiveness of other chemicals". It's a blue, flour texture stuff...not sure if we even need it, but it came with the startup kit. Maybe it's part to blame, who knows. Well, it sounds like your sanitizer level is just fine, so it doesn't seem to be a microbial problem. Your pH is on the high side though. If the Ultra-Spa Conditioner is a borate salt solution, and your hardness is on the high side of the OK range (200 to 300 ppm), with your pH on the high side too, you're probably experiencing calcium precipitation, which would definitely cloud the water and could be hard to filter out without a clarifier. Does the Ultra-Spa Conditioner package list the ingredients? If it is borates, it could easily raise your saturation index to the point of precipitating calcium carbonate, considering where you're starting from. Your description of the "billiions of little white particles" fits this explanation. If that's what happened, you might want to drain 1/4 to 1/2 of the water and refill, then forego using the conditioner. It may be necessary to change the filter too. Then try to keep the pH below 7.6, and you shouldn't have the problem again. Don

What sanitizer are you using? Cloudy water is likely due to either bacterial growth, due to inadequate sanitizer, or preciptiation of minerals, which shouldn't occur unless there is a drastic change in the chemical composition. What happens when you leave the pumps off for a few hours? Does the cloudiness settle out, disappear or remain? FYI, dissolved solids don't cause cloudiness, suspended solids do. And filters can't remove dissolved solids, they can only remove suspended solids. The Micropure filter won't filter out bacteria even though they are suspended because they are too small to be caught by the filter, unless you flocculate them, which is what your clarifier does. Some suspended minerals are also too small to be filtered by a 1 micron filter like the Micropure MF-170 unless flocculated, so you could be dealing with mineral or a microbial haze, but the microbial haze is more likely if it occured suddenly with no drastic change in water chemistry. Don

Hi Kammie, I can't be sure just by looking at the photo, but that looks like it could be "soap scum", which is produced in a spa that has low hardness, pH and/or alkalinity. Is that residue sort of soft and flaky or gooey, or is it hard and brittle? I assume you're using chlorine as a primary sanitizer, is that right? Any issues with water clarity? Don

That's a nice feature. My spreadsheet isn't intended for novice users and people aren't usually switching back and forth between U.S. and Metric -- they usually pick one and stick with it. Though I know how to attach a macro to a button, I'm not even sure how to attach one to a pull-down menu selection (in Excel) and it would take a macro to "update" a type-in field (as opposed to a calculated field that could simply look at the pull-down menu setting). I probably won't be changing this. Hi Richard, FYI Excel does have the ability to run macros when cell values change. Here's a web page describing the ability: http://www.ozgrid.com/VBA/run-macros-change.htm Don

Ah, OK, thanks - it works as advertised. I fill my gas tank with gallons, bake bread with cups, teaspoons and tablespoons and complain about the weather in degrees Fahrenheit. But due to my background I like to work metrically when dealing with chemistry. Now I know how to do it with your spreadsheet. I continue to be impressed as I use more features of it, and haven't found any errors yet in the formulas. Don

I'll take a crack at this one. Peroxysan is not particularly new. It, or similar formulations, have been around for over 20 years and are used successfully as an antimicrobial agent in several applications. The active ingredients are peroxyacetic acid, also called peracetic acid, and hydrogen peroxide, and the other major components are water and acetic acid. Peroxyacetic acid is always sold in solutions containing hydrogen peroxide and acetic acid, which stabilize it and prevent potentially violent decomposition. What may be new is the attempt to market Peroxysan as a primary disinfectant for spas. Peroxysan is approved in the US for disinfection of hard surfaces (i.e., in food processing plants) and is used for treatment of recirculating water in cooling towers. It is not, however, approved as a disinfectant for swimming pools, spas or public water supplies in any country as far as I know. In the US the federal government cannot yet force homeowners to adhere to particular regimes for pool and spa maintenance, but does enforce standards for public pools, spas and water supplies. The homeowner is well advised to steer clear of products that are not approved for municipal and commercial use, or at least proven effective by substantial, relevant data, IMHO. There are plenty of people out there who will take your money in exchange for worthless products. I'm not saying Peroxysan is not effective as a spa disinfectant - all I am saying is that it's not approved and not proven effective for spa use. There seems to be very little information available related to actual, real world experience with using Peroxysan in spas, and the information I was able to find on the internet unanymously concludes that its effective application is difficult at best. There is also very little information on the Peroxysan web site at http://www.peroxysan.com, other than marketing hype. That site talks about the hydrogen peroxide in Peroxysan, probably because use of hydrogen peroxide in spas is well established, though not as a primary disinfectant. They don't even mention the primary active component, peroxyacetic acid (at least I can't find it mentioned), probably because anyone who looked it up (try http://en.wikipedia.org/wiki/Peracetic_acid) would be leery of using it at home. Safe use of peroxyacetic acid would require the applicator (that's you) to wear heavy rubber gloves and full face goggles at least, and preferably a full length heavy neoprene apron, to avoid potentially dangerous burns from skin contact due to splashing and spills. Don