chem geek
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Posts posted by chem geek
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If the ozonator is working, then maintaining a bromide bank -- around 30 ppm bromide -- should have the ozone maintain a background level of bromine. The ozonator should oxidize bather waste so need only half the amounts (or less) that I indicated when there is bather load. Then the issue will be what to do if the spa has heavy use. It will need some sort of oxidizer added to it to create more bromine -- chlorine or MPS.
If you shock, it goes high not just to normal. The problem with adding too much is that it will take time to get lowered but if you add the right amount after a soak then it should drop down to normal within 24 hours. So managing a vacation rental is tough, but at least the ozonator helps.
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In a bromine spa you presumably have created or built up a bromide bank so the MPS will slowly oxidize bromide to create more bromine. So the dosage is really to create a bromine level or to add enough to oxidize bather waste.
The rough rule-of-thumb with no ozonator is that every person-hour of soaking in a hot (104ºF) spa requires around 3-1/2 teaspoons of Dichlor or 3-1/2 fluid ounces of 8.25% bleach or 7 teaspoons of non-chlorine shock (43% MPS) to oxidize bather waste. That is true whether it's a chlorine or a bromine or a Nature2 silver ion spa. With an ozonator and heavier bather load (i.e. soaking every day or two) these amounts might be only half as high. The real rule is to add whatever is needed so that you end up with a residual of disinfectant 24 hours later and then maintain that level prior to your soak. That's usually around 2 ppm Free Chlorine (FC) for chlorine or 4 ppm Total Bromine for bromine.
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That's an option that might work, but the higher salt content (usually 2000 ppm for a spa) will be more corrosive and might void a warranty if the spa is fairly new. If the spa components use higher quality stainless steel (316/316L, not 304) and have a corrosion-resistant heat exchanger in the gas heater (curpro-nickel alloy or titanium, not copper) then a saltwater chlorine generator will probably be OK, such as the ControlOMatic Technichlor.
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Because Cyanuric Acid (CYA) is used with chlorine, the chlorine doesn't actually outgas much faster than bromine. When people say chlorine outgases faster, that is when there is no CYA. With CYA, that changes the rate substantially.
It may be, however, that the outgassed bromine is not as strong a disinfectant against mold than chlorine would be. To be honest, I don't know, but I haven't seen this mold problem reported much so whether this is more likely with bromine vs. just a statistical fluke, I can't say.
Mold needs moisture, warmth, and organic substances (i.e. a food source). You may have greases/oils or biofilm acting as a food source on some spa surfaces. So after you've used a disinfectant like bleach to clean them, you should probably use a strong surfactant such as Ahh-Some not only for your spa water but also to use to thoroughly clean surfaces. This may help make mold growth take longer since it will take a while to buildup organics on the surfaces, at least if it's only evaporated water reaching those surfaces and not direct spa water which of course contains lots of organics leftover from bather waste.
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There is no need to add baking soda to increase TA in multiple steps, but if you increase TA then you will increase the rate of pH rise from carbon dioxide outgassing. You should only have the TA be higher if you are using net acidic sources of chlorine such as Dichlor (it is fairly neutral upon addition, but chlorine usage/consumption is acidic).
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See also this post. Aeration of the water will outgas carbon dioxide causing the pH to rise. If you add acid to lower the pH, then the TA gets lowered as well. You don't want the TA to get too high or else the pH will rise even faster. It sounds like what you need is supplemental pH buffering. Are you using 50 ppm Borates (usually from boric acid)?
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What doesn't make sense? It's possible for the pH to be higher yet the TA to be low. A low TA just slows down the rate of pH rise from carbon dioxide outgassing, but does not completely stop that rise. If one wants to further slow down the rate of rise one can use 50 ppm Borates (usually added from boric acid) for additional pH buffering.
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You do not need those other chemicals. The Nature2 silver ions would be used with MPS for a chlorine-free disinfection, but since your wife can't tolerate MPS there isn't the need for the silver ions. If you want to use them up, they won't cause any harm with the chlorine and will be a backup for slow disinfection if the chlorine level went to zero. The Rendezvous Protect Plus would only be needed if you had metals in the water such as from a well and normally get metal staining. The GLB Natural Clear Enzymes should not be needed unless you had dirty bathers with lots of oils and you were impatient to have them cleared from chlorine and circulation/filtration.
The ozonator will increase your chlorine demand in between soaks so if you don't use the spa regularly then that can increase your chlorine usage. If you use the spa every day or two then an ozonator is helpful to oxidize your bather waste so you use less chlorine.
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A saltwater chlorine generator produces chlorine. It's just an automated way of doing so. It is not chlorine-free, if that is what you were looking for.
So do you have a whole-house or a shower dechlorinator? If not, then depending on where you live she is already getting exposed in the shower or bath to either chlorine or monochloramine at higher active levels than found in a spa with Cyanuric Acid (CYA) in it.
Using chlorine at low levels is probably your best bet. Just start the soak with 1-2 ppm FC with 30-40 ppm CYA. See Nitro's Guide to Water Maintenance at the top of this forum.
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You can use Dichlor or MPS with Nature2. The main reason people use MPS is because they don't want to soak with chlorine, but usually some chlorine is needed every week or so to keep the water clear, particularly if there is no ozonator.
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With infrequent spa use the easiest ways to maintain a disinfectant level in between soaks is to use either 1) bromine tabs or 2) a saltwater chlorine generator. Another possibility is to use Nature2 with MPS (non-chlorine shock) since is lasts longer than chlorine, especially if you have an ozonator (ozone reacts with chlorine).
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If you maintain the proper FC/CYA ratio and have decent circulation, you won't get green or black algae, period. If the FC/CYA ratio is 7.5% or higher, then chlorine will kill algae faster than it can grow regardless of algae nutrient (phosphates or nitrates) level and temperature.
The FC/CYA ratio is proportional to the active chlorine (hypochlorous acid) level).
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He is assuming that the ozonator will disinfect in between soaks. How is that supposed to happen? Is the ozonator on and therefore the circulation pump on ALL THE TIME? Ozone has a half-life of around 20 minutes or so and usually there isn't a significant residual in the tub anyway -- otherwise it would outgas.
You should have a RESIDUAL DISINFECTANT in the spa water. The EPA has approved products for spas that have only one of the four following chemicals: Chlorine, Bromine, Baquacil/biguanide/PHMB, and Nature2 (silver ions) with MPS (non-chlorine shock).
Since you won't be using the spa every day and since you have an ozonator, bromine tabs would be easiest to provide a residual unless you got a saltwater chlorine generator.
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You've both got reasonable plans. As for whether you want to use MPS vs. chlorine, just keep in mind that MPS without silver ions (i.e. without using Nature2) is not an EPA-approved disinfectant so for Zeta MPS would disinfect. Unfortunately, while MPS oxidizes some chemicals, it doesn't do well with ammonia which is in sweat and urine. Nevertheless a mix is reasonable, but it's really up to you. At least using some MPS may let you use less chlorine and perhaps have less smell of chlorine and some chloramines as a result.
This is one of those things best determined by trying it out different ways and comparing. I suspect that using a mix of chlorine and MPS will work well to minimize the noticeability of chlorine while still providing good disinfection. Note that the persulfate minor component of MPS (not monopersulfate which is the primary component) is irritating to some people, but that in the presence of silver ions it gets degraded which is why MPS with silver ions is usually not irritating.
Also note that having an ozonator helps tremendously in a situation with high bather load. However, ozonators are usually turned off whenever the jets are run to avoid ozone outgassing. So keep that in mind that you may need "jet off" periods if you want the ozonator to run (if it runs all the time when such jets are off). Unfortunately, most spas don't have explicit controls nor notification about running the ozonator.
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I just want to be clear about the pros/cons/risks of using low vs. higher chlorine levels at the start of a soak. If one starts with 1-2 ppm FC, then the smell of chlorine and formed chloramines should be minimal during a soak, but unless it's a low bather load (i.e. just one person, larger spa, short soak) the chlorine may run out during the soak as it oxidizes bather waste (sweat and urine, mostly, but also your skin and swimsuit and some outgassing especially when jets are used).
While there may be monochloramine formed that will continue to more slowly inhibit bacteria, when the FC is at or near zero you don't have fast pathogen kill times so do not have protection from person-to-person transmission of disease. That's the downside risk of not starting a soak with enough chlorine or otherwise maintaining it's level (say, with a saltwater chlorine generator). The risk is lower when sharing a spa with family members since you may be sharing bacteria and viruses with them outside the tub, but to minimize risk clean your bums thoroughly as that is where most of the riskier pathogens come from (i.e. from fecal matter).
It is true that bacteria generally take 15-60 minutes to double in population so you aren't going to get uncontrolled bacterial growth in the hour one is in the spa. However, that is not the same as preventing bacteria or viruses from transmitting from one person to another via the water.
The EPA rules that are specified on the labels of disinfectant products tell you to maintain an FC level since these rules are designed for efficacy and safety.
As for the least expensive source for the Taylor R-0867-C reagent is Amato Industries. Even the kit on Amazon is $23, not $30 and the reagent $10 so about the same as Amato.
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Thanks Matt. It's just hot tub care, not world peace, but I appreciate the sentiment.
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Hot Springs ACE Vanishing Act will lower CH levels, though is not cheap. It is normally sold for use with the ACE system that requires low CH but you can use it to lower CH for any reason. A water softener may be more economical in the long run.
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As described in the Nature2 SPA Mineral Sanitizer Owner's Manual, you can use either MPS or chlorine with the system. MPS is more expensive but obviously doesn't have any chlorine smell nor product any chlorinated disinfection by-products. It's not as broad an oxidize (doesn't oxidize ammonia very well from sweat and urine) so usually if you use MPS you'll need to use chlorine on occasion, but the way the spa dealer suggested using chlorine and using MPS weekly is fine as well. It's up to you.
The Dichlor-then-bleach method takes some effort to set up, but once done it's easy if you soak regularly. If you only use the spa on weekends, it can be more trouble since you would need to add chlorine in between soaks. If you have an ozonator, then ozone destroys chlorine (forming chloride and chlorate) so would require even more frequent chlorine addition, though it works well in more heavily used spas (i.e. used every day or two).
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It is the low TA with the 50 ppm Borates that combined help stabilize pH that would otherwise rise from carbon dioxide outgassing. So that will help in any situation where you use hypochlorite sources of chlorine or a saltwater chlorine generator or bromine tabs or using hypochlorite to make bromine from a bromide bank.
There is no interaction between the borates and CYA or other chemicals in the spa. The borates are an independent pH buffer.
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I don't hate any product. I just tell you what's in it and what the consequences are for using it. Leslie's Chlor-Brite is Dichlor as shown in the MSDS that says "Sodium dichloroisocyanurate dihydrate 98-100%". So if you need Dichlor, then there's nothing wrong with using that product.
ANY source of Dichlor will add 9 ppm CYA for every 10 ppm FC. That's a chemical relationship that has nothing to do with the specific product brand. For Trichlor, 6 ppm CYA is added for every 10 ppm FC.
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No health downsides to CYA at the concentrations used in pools and spas. Of course, if one has too much CYA in the water and doesn't raise the FC level proportionately, then the active chlorine level can get too low with its obvious health consequences (i.e. inadequate disinfection). Using Dichlor-only builds up CYA which is why the spa water needs to be replaced more frequently using that method compared to Dichlor-then-bleach.
As to whether the Dichlor-then-bleach method will work well for you, it depends on your spa usage and whether you have an ozonator. If you use the spa infrequently (say only on weekends) and you have an ozonator, then you'll be having to add chlorine frequently pretty much every day which is obviously more work. If you use the spa every day or two, then adding Dichlor or bleach after a soak so that you measure a small residual (1-2 ppm) at the start of your next soak is probably not too much work.
Certainly a saltwater chlorine generator is easiest once you dial in the right level for background generation of chlorine in between soaks.
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You don't have to add chlorine to get to 10 ppm. Just add enough to maintain a small residual of 1-2 ppm. That becomes tricky if you use the spa for a longer time. One person-hour with 3-1/2 teaspoons Dichlor (assuming 0.58 ounces weight) in 415 gallons would use 5.8 ppm oxidizing bather waste but over 24 hours, mostly in the first 8-12 hours. As apostlej2015 notes, the chlorine doesn't drop that much in the hour you are in the spa, but it does drop.
The ideal situation has chlorine added continuously to maintain an FC level but that's impractical if you aren't using a saltwater chlorine generator (assuming it could keep up). So a compromise is to start out somewhat higher in FC but not so high as to be unpleasant and then check on the FC every so often and increase it. The instructions on the Dichlor probably say the maximum FC being in the spa is 4 ppm for pools or 5 ppm for spas. You could start with that then check in an hour (or less if people happen to be out of the spa or don't mind getting out more frequently) and add more chlorine to raise to that level again. 10 ppm would be too high and likely unpleasant from too much chlorine smell (CYA will moderate chlorine's strength so it won't necessarily feel too strong), but again the EPA limit is lower than this.
Fortunately, the chlorine gets spread throughout the spa quickly if you have circulation so you should be able to re-enter in just a couple of minutes.
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You can use spa water that has been chlorinated as a water source for your grass area. You just do so when the chlorine level is low as would be the case just before you would do a soak. Municipal tap water that is also used for watering has up to 4 ppm chlorine in it though usually it's closer to 1 ppm. Most municipalities have switched to using monochloramine instead, but the point is that for decades tap water had chlorine and watered plants with no issues.
MPS is net acidic so the pH would drop when using it and then rise again from aeration in between its use. With the Dichlor-then-bleach method the pH would tend to rise from aeration (carbon dioxide outgassing) so to combat that you lower your TA to around 50 ppm and then use 50 ppm Borates (usually by adding boric acid) for additional pH buffering.
If you do the Dichlor-then-bleach method properly, you shouldn't smell much chlorine during the soak because you should be starting your soak with around 1-2 ppm FC and you should have 30-40 ppm CYA in the water that moderates chlorine's strength. You then add chlorine (or a mix of chlorine and MPS -- see below) after your soak to oxidize the bather waste. You should have LESS chlorine smell during your soak than you did before because you said you added Dichlor granules before your soak so probably had the chlorine higher than you will be doing (though it depends on the level of chlorine you were using and over time the increasing CYA level would have over-moderated chlorine's strength).
If you want you can use a separately added mix of MPS and bleach after your soak. Without the Nature2 stick with its silver ions you can't use the MPS alone for disinfection, but you can use it to help oxidize bather waste. So you'll still want to add chlorine as well after your soak in an amount such that you still measure a low chlorine residual just before your next soak. Basically, this will be similar to what you did with Nature2 except you'll be using bleach instead of Dichlor (except at first to build up some CYA) and only add it after your soak and not before (unless your chlorine level is too low before your soak, but you should not let it get that low).
Note that if you use MPS, that it lowers pH and TA so you can try targeting 80 ppm for TA to start out and see if that works well for a reasonably balanced pH. If the pH tends to fall, then raise the TA (usually by adding baking soda). If the pH tends to rise, then you can let the TA drop but not below 50 ppm. In your 360 gallon tub, every tablespoon (3 teaspoons) of MPS will lower the TA by about 2.6 ppm.
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That's up to you if you believe you have a serious contamination problem. Usually Ahh-Some will be enough.
Can't Keep Bromine Levels Higher Than Zero
in Hot Tub Water Chemistry
Posted
It sounds like there is a lot of oxidizer demand in that spa. I suggest you use Ahh-Some to remove greases, oils, and biofilm.