tds bogus or true???????

[waterbear]

RavenNS,
Since spas are drained and refilled every 1 to 3 months TDS is not an issue if they are properly maintained. The problem startes when people start dumping unnecessary defoamers, clairifies, fragrences, etc. into the water. Also, many people, including dealers, just don't understand bromine chemisty. Look at the number of people who just put bromine tabs in a floater and don't put sodum bromide in the water with each refill for an example and then wonder why they can't maintain a sanitizer level.....or the number of people who don't realize that chlorine is probably the most effective way to shock a bromine spa (or that almost all bromine tablets contain chlorine also for this reason!)

[chem geek]

Using 1500 ppm, it is designed to maintain a NON-USE chlorine residual for spas up to 800 gallons.

Sean,

Is the purpose of the chlorine primarily to regenerate bromide ion (Br-) back into hypobromous acid (HOBr) on a continual basis (which is what KMPS would do as well, though KMPS is also useful for oxidizing organics before chlorine does to prevent potentially smelly chloramine formation)? Or is it to also supplement the hypobromous acid for oxidation and disinfection? The "NON-USE" seems to imply that it is for the former, not the latter.

Richard

[RavenNS]

First of all, Chem Geek, absolutely no offense taken... I didn't write the article, I just thought it was worth reading (especially for newbies to TDS).
regarding adding chlorine to bromine: I thought we ( waterbear & chemgeek & I) discussed this as a bad idea in another thread lol

I dump the tub water about every three or four months, although timing can be quite important in winter... no one wants to do the empty-refill maintance in a blizzard.
I do use quite a bit of chemicals for start-up ( not just throwing some pucks in). I also have two chemicals for cleaning the filters which I do every month.
not to mention " tub clean" a very acidic chemical that you run through prior to draining.. ( eat your skin off! & so stinky too)

My primary hot tub, although outdoors, is essentially an almost "closed system". The cover is always on, unless we are in it... ( steam doesn't even escape it in the coldest days of winter). It is a completely independant system & this may make it "behave" differently than waterbear's tub which is part of his pool system.

I don't "shock" my tub per say ( except for start-up), but I do bring the levels up quickly ( & probably in-fact shocking it); We often throw some "bromoblast" in the tub as we get into it. We actually prefer to keep our tub at 10+ppm; this really helps my DH with some troubling skin conditions that he used to take medication for, prior to getting the Tub.
( and if you have any pus sores, the high bromine seems to draw out the infection & help the healing process as it dries out the sore & seems to close it up too.... Also cures diaper rash! lol... & strips my hair of colour beautifully.. )

As I said before I prefer the tub at a TDS of 800- 1000 ppm.I would be happy to just partially drain & refill, just to keep the TDS at that level.- I don't like the feel of high TDS water ( or low TDS water for that matter...lol). But I worry about the safety issues of residual bacteria living in the "pass-through" area of the motor/heater... ( I have a large amount of piping there... it may be like a tankless water heater, but it is several feet of piping)

( why is it difficult to believe that when there is tons of crap in your tub, or high TDS, that your sanitizer might get 'busy" with all that & that it won't be as effective? is it not plausibile?)

( also note that if you add fragrance for every tub-ride, you'll hit the high TDS mark very fast as well. & I suspect that the fragrance binding/bonding materials interfer somewhat with the sanitizers, although I have no proof of that. lol)

So maybe it isn't "important" if you are draining every three months... but for those people who don't; TDS monitoring is a good reminder of when to drain.

[chem geek]

( why is it difficult to believe that when there is tons of crap in your tub, or high TDS, that your sanitizer might get 'busy" with all that & that it won't be as effective? is it not plausibile?)

( also note that if you add fragrance for every tub-ride, you'll hit the high TDS mark very fast as well. & I suspect that the fragrance binding/bonding materials interfer somewhat with the sanitizers, although I have no proof of that. lol)

Normally dissolved substances, specifically charged ions, in water only interfere with chemical reactions due to what is known as "ionic strength". With sufficiently high TDS, this does in fact start to shift equilibrium towards charged ionic species since their "activity" is reduced relative to their actual concentration. My spreadsheet actually calculates all of this. However, the effect is very small in terms of its effect on chlorine concentration (though not on LSI or water balance) and essentially can be ignored for the ranges of TDS we are dealing with. It would be very important in sea water, but even salt SWCG pools do not have enough TDS to be of concern.

As an example, in a pool without CYA and with 2 ppm chlorine, 7.5 pH, 100 TA, 300 CH, 510 TDS (the minimum with these other parameters), and a temperature of 80F, this results in 0.968 HOCl (now correctly interpreted in ppm Cl2 units as all chlorine is measured due to historical convention). If I increase the TDS to 3500, then the HOCl drops to 0.909 which isn't a huge change.

Interestingly, if I repeat the above with CYA of 30 ppm and use 3 ppm chlorine, then I get at 525 TDS (again, the minimum which is higher due to the CYA), 0.042 for HOCl. If I increase the TDS to 3500, then the HOCl drops to 0.041 which is hardly a change at all.

The reason that changes in TDS have virtually no effect on HOCl in the presence of CYA is that the CYA acts like a chlorine (specifially an HOCl) buffer and resists changes in HOCl level due to outside factors. Specifically, the dominant equation where CYA buffers HOCl has charged ions of equal strength (charge) on both sides of the equation so changes in ionic strength due to TDS mostly cancel each other out. Without CYA, it is the HOCl/OCl- relationship that is affected and here there is charge on one side of the equation and no charge on the other.

Now in spite of what I just said it is of course possible that some forms of organics that get into the water may behave somewhat like CYA and tie up the chlorine and reduce its effectiveness. However, any such substance would have to also report its chlorine in the standard chlorine test for FC and would have to not be destroyed (oxidized) by the chlorine. Chlorine bound to CYA gets reported as FC since it is released from CYA in a matter of seconds. So yes, it is possible for some other organic compounds to behave in a similar fashion, but most are simply 1) combined with chlorine and stay that way as "combined chlorine" until fully oxidized (and are measured as the CC part of TC, but are not in FC) or 2) are not affected by chlorine at all. Obviously CYA is an "organic substance" that inhibits chlorine so certainly it is possible for other substances to behave this way as well.

So again, it is not the high TDS in and of itself that is a problem, but rather the fact that a high TDS may indicate older water that has more organics in it (in addition to salt) and some of these organics may interfere with chlorine's effectiveness. My hunch, however, is that for most standard organics that get into the pool or spa, that few if any inhibit chlorine's effectiveness (assuming you do not allow combined chlorine to build up since obviously that is chlorine that is not effective).

Richard

[KurtV]

( why is it difficult to believe that when there is tons of crap in your tub, or high TDS, that your sanitizer might get 'busy" with all that & that it won't be as effective? is it not plausibile?)

I guess the reason I find that hard to believe is that every pool with an SWG is operating at or above the "limit" of 3000 ppm. Most SWGs recommend something in the neighborhood of 3000 ppm of salt alone and some are designed to work at 6000 ppm and even higher. I've yet to hear from anyone with an SWG who didnt rave about it.

[Poolsean]

Richard,

It's primarily a chlorine generator but with additional NaCl and NaBr it can be a bromine generator. The "Non-Use" application means that the KMPS is used up front to create a residual for use, then to clean it up by oxidizing the combined chlorine (or combined bromine)...so actually, the latter.

[waterbear]

First of all, Chem Geek, absolutely no offense taken... I didn't write the article, I just thought it was worth reading (especially for newbies to TDS).
regarding adding chlorine to bromine: I thought we ( waterbear & chemgeek & I) discussed this as a bad idea in another thread lol
Wrong, I have stated many times that chlorine (read bleach) is probably the BEST oxidizer to use in a bromine system!
I dump the tub water about every three or four months, although timing can be quite important in winter... no one wants to do the empty-refill maintance in a blizzard.
I do use quite a bit of chemicals for start-up ( not just throwing some pucks in). I also have two chemicals for cleaning the filters which I do every month.
not to mention " tub clean" a very acidic chemical that you run through prior to draining.. ( eat your skin off! & so stinky too)
If you are so concerend about cleaning out the pipes I would suggest an enzyme product....they work great and are not toxic!
My primary hot tub, although outdoors, is essentially an almost "closed system". The cover is always on, unless we are in it... ( steam doesn't even escape it in the coldest days of winter). It is a completely independant system & this may make it "behave" differently than waterbear's tub which is part of his pool system.
I owned a portable hot tub for many years before I built my present pool/spa combo and kept it on both bromine and chlorine at different times.
I don't "shock" my tub per say ( except for start-up), but I do bring the levels up quickly ( & probably in-fact shocking it); We often throw some "bromoblast" in the tub as we get into it. We actually prefer to keep our tub at 10+ppm; this really helps my DH with some troubling skin conditions that he used to take medication for, prior to getting the Tub.
( and if you have any pus sores, the high bromine seems to draw out the infection & help the healing process as it dries out the sore & seems to close it up too.... Also cures diaper rash! lol... & strips my hair of colour beautifully.. )
Shocking is really a misnomer for a bromine system. When you add the oxidizer, whether chlorine, MPS, or ozone it reacts with the bromine ions in the water to form hypobromous acid....your active sanitizer. Tabs contain both bromine and chlorine or bromine and MPS so as they dissolve they add both to the water. If your bromine levels are low try adding some bleach and watch them shoot up (if you have a bromine reserve in the water) if you don't believe me!
As I said before I prefer the tub at a TDS of 800- 1000 ppm.I would be happy to just partially drain & refill, just to keep the TDS at that level.- I don't like the feel of high TDS water ( or low TDS water for that matter...lol). But I worry about the safety issues of residual bacteria living in the "pass-through" area of the motor/heater... ( I have a large amount of piping there... it may be like a tankless water heater, but it is several feet of piping)
and has a constant flow of water with residual sanitizer passing through it whenever the filtration system is running!
( why is it difficult to believe that when there is tons of crap in your tub, or high TDS, that your sanitizer might get 'busy" with all that & that it won't be as effective? is it not plausibile?)
because there is no chemisty to back it up!
( also note that if you add fragrance for every tub-ride, you'll hit the high TDS mark very fast as well. & I suspect that the fragrance binding/bonding materials interfer somewhat with the sanitizers, although I have no proof of that. lol)
do you really need that crap in your tub? It just means that you will have to drain your tub more often....and the ingredients probably won't show up on a TDS test. That measure ions in the water...non ionic additions to the water won't register on the test!
So maybe it isn't "important" if you are draining every three months... but for those people who don't; TDS monitoring is a good reminder of when to drain.

With both pools and hot tubs there are certain maintenace rules to follow if you want trouble free performance. With hot tubs it means draining and refilling on a regular basis. A good indication that you need to do this is when the tub starts to foam or you see heavy scum starting to collect on the water line

[RavenNS]

Okay, once again... I keep my tub at a minimum of 10ppm bromine. I do not need to shock as per industry standards in Canada.
I'm am not really worried about residual bacteria, it's just something that I think about because a family in my province was hospitalized due to that exact problem ( hot tub bacteria out of control & the kids almost died! - it was an indoor tub which was not properly sanatized prior to draining & clearly not sanatized properly when they refilled it months later... nasty bacteria was found in the piping by investigators).

I follow all the recommendations of my tub from the manufactor & have had perfect water in both of my tubs, always ( wish I could say that about my pool...lol).
( waterbear, I think you missed that I was being sarcastic in my last post..lol , sorry )

I don't put extra crap in my tub ( fragrances etc.), although I would love to scent my pool with Hawaiian Lily..lol, ( love that one; can't help but open a bottle & sniff it every week when I visit the hot tub store) ( btw, I have no intention of putting fragrance in my pool, okay? )

The question of this thread was asking if high TDS should be addressed & the tub dumped. It is my opinion that the answer is Yes.
It is only my personal opinion that a TDS of over 1450 in a hot tub, makes the water really yucky & not performing ( or feeling) as it should. Industry standards & tub manufactors concur with this opinion, however, chemists may or may not.
I further stated that I would keep my tub at 800- 1000 TDS ( if it were possible), as by my observations, that is when the water performs best ( for me & mine).

so again, the question of the postee was , should he dump his tub water?...
I still feel that he should have a second test done at another store & see what the levels are... if the TDS is high, I still believe he should drain & refill, regardless if the water is "fresh".
And since the postee had water trucked in, I would consider either going with a different water company, or asking them to check the TDS prior to delivering.... ( which makes me wonder if it could be picking up residual particles from not having the truck cleaned out throughly...)

( ps- I have never seen my tub start to foam or had scum-lines... maybe because of regular maitenance or maybe because I drain the tub when it reaches 1200 TDS...)

[waterbear]

Okay, once again... I keep my tub at a minimum of 10ppm bromine. I do not need to shock as per industry standards in Canada.
As I said before, shocking is NOT what is done with a bromine system. When you add oxidizer you are converting bromine ions back into hypobromous acid....whether this is done with chlorine, MPS, or ozone is moot. The action of the added oxidizer creates hypobromous acid from the bromine ions. If chlorine is used the hypochlorous acid is immediately converted into hypobromous acid. The effect of 'adding shock' to a hot tub (as it is commenly referred to) is to raise the bromine level in the water when it has dropped. Adding more bromine to the water will not accomplish this unless an oxidizer is also present. Basic bromine chemistry. If you use tabs in a floater then you are adding both bromine and clorine or bromine and MPS at the same time....depends on the tab you use whether it contains chlorine (most do) or MPS (only one brand that I am currently aware of)
I'm am not really worried about residual bacteria, it's just something that I think about because a family in my province was hospitalized due to that exact problem ( hot tub bacteria out of control & the kids almost died! - it was an indoor tub which was not properly sanatized prior to draining & clearly not sanatized properly when they refilled it months later... nasty bacteria was found in the piping by investigators).
This is why proper sanitation of a hot tub or pool IS so important...and why I don't like copper/silver systems that say you can use reduced chlorine levels or only MPS in a hot tub! With bromine levels of 10+ ppm your tub should be very well sanitized....I would worry about developing bromine sensitivity with that high a level, however....bromine is a known sensitizer and the biggest problem with it's use is that many people can get a reaction from it. Some exhibit this right away...others develop it over time with exposure to the bromine. Also, it seems that 'hot tub folliculitis' is more commen in bromine santized spas.
I follow all the recommendations of my tub from the manufactor & have had perfect water in both of my tubs, always ( wish I could say that about my pool...lol).
Hang around on the forum and you will find that your pool is actually EASIER to maintain then your hot tub....I speak from experience!
( waterbear, I think you missed that I was being sarcastic in my last post..lol , sorry )

I don't put extra crap in my tub ( fragrances etc.), although I would love to scent my pool with Hawaiian Lily..lol, ( love that one; can't help but open a bottle & sniff it every week when I visit the hot tub store) ( btw, I have no intention of putting fragrance in my pool, okay? )

The question of this thread was asking if high TDS should be addressed & the tub dumped. It is my opinion that the answer is Yes.
It is only my personal opinion that a TDS of over 1450 in a hot tub, makes the water really yucky & not performing ( or feeling) as it should. Industry standards & tub manufactors concur with this opinion, however, chemists may or may not.
I further stated that I would keep my tub at 800- 1000 TDS ( if it were possible), as by my observations, that is when the water performs best ( for me & mine).

so again, the question of the postee was , should he dump his tub water?...
I still feel that he should have a second test done at another store & see what the levels are... if the TDS is high, I still believe he should drain & refill, regardless if the water is "fresh".
He also said that he has the same water tested a few days later and the TDS was fine AND that the tub had just been filled....indicates a testing error. Also some places are using test strips to test for TDS....not very reliable. If you are maintaining your your tub properly and draining on a regular interval then the TDS test is not necessary.
And since the postee had water trucked in, I would consider either going with a different water company, or asking them to check the TDS prior to delivering.... ( which makes me wonder if it could be picking up residual particles from not having the truck cleaned out throughly...)

( ps- I have never seen my tub start to foam or had scum-lines... maybe because of regular maitenance or maybe because I drain the tub when it reaches 1200 TDS...)
Which I bet is around every 3 months or less. The effects of high TDS will be such things as foaming or scum. TDS is really only usefull as an approximation of how 'old the water is. There are hot tubs that are sanitized by SWGs so the TDS measurment for them will be totally useless since they will have a TDS of the salt level (usually around 3000ppm) plus whatever ionic solids are dissolved in the water such as calcium, magnesium , sodium , potassium, chloride, bromide, etc. In some reagions the fill water can have a TDS higher than the recommended levels and yet the tub or pool can be operated and maintained without any problems. In acutal practice TDS is about as useful a measurement as is the Langelier Saturation Index (which has been the topic of MANY discussions on here.

One final note....you stated that your hot tub is essentially a 'closed system'. You forgot the main thing that makes this assumption wrong....the bathers entering the tub. IF you never used it and no one ever got into the tub between each drain and refill then it would approximate a closed system much better. The first time someone enters the tub it stops being a closed system because of what the bather introduces into the water (sweat, fecal matter, body oils, etc)!

[turbottt1]

For the reord. I would love to see test readings of 1000-1500. When we use to worry about the tds measement I'm talking 5000. Read second post. New water, only chems. needed, and two bathers. Test results 2500-5000. Yes there were strips used. First thing you say. strips are no good. We always take a pool sample with us too.[ 1250-1500 range. We go to the local pool store and also up to our artic dealer results close to the same with multi. test done each time. Our tub is sitting at 5000 right now. I dare you to fine cleaner, better smelling, and easier water to care of anywhere. no foam, no scum line nothing and we use no defoamers, scumballs,etc. As far as cleaning the tub I'm not sure how everybody else does it but we first run the cleaning product[ fresh start] for 24hrs. before dumping the water, dump the water, suck out all lines, flush with clean water all jets, filters,lines, etc. which fills the foot well and dump that water, suck lines, etc again, take our chlor. shock mixed wipe down all surfaces including the bottom of the cover and refill. We have had the same trucking compant bring us our water multi. times this year including 25" of water for the pool.[ 30' round] We have discovered that we have been adding sodium bromide to the water weekly. Could we be picking up a false reading because of over high levels of this???? steve