The Salt Dellima

[stuart]

Chem Geek,
You're correct....I should have said tri-chlor and cal-hypo are "un-stable" in portable spas from my experience. I realize that stabilizer is added however, from my field experience, I can tell you that they are extremely unstable in a hot tub environment.

There are both plumbing manufactures and PVC glue manufactures that warn against the use of Cal-Hypo with their product.

I just worked on a spa that had relatively new plumbing yet after 4 months of the customer using tri-chlor tablets, the flex was brittle and blistered inside. it actually split the flex between ribs at the pump.

As always I enjoy your posts and your obvious knowledge of water chemistry however, I'm interested in your background and field experience with hot tubs vs. pools? There is no doubt that you have the science of it down, but I know that many of us see radical differences working on hot tubs daily and have learned the hard way that pool chemistry is a whole different animal.

I'm also interested in your thoughts on what you've seen in the field from different brands of spas and the affect of tri-chlor or cal-hypo on their plumbing.

Thanks ahead of time....

[chem geek]

I own a pool, not a spa, and I do not work in the industry.  As for field reports, they come from the tens of thousands of people reporting on forums and from service people reporting on such forums as well.

Trichlor inline chlorinators are made of PVC but that's hard PVC and not the flexible kind of piping which may be more susceptible to acidic conditions.  Having Trichlor introduced in a way where it gets well mixed should not be a problem, but having it in a skimmer when circulation is off can have the high chlorine low pH conditions migrate to materials that are not resistant and can have problems.  This is why even in pools one should not put Trichlor in the skimmer because the pump isn't usually running 24/7.  For spas, Trichlor is normally not used because it dissolves too quickly and if people don't watch the drop in pH and TA, then then the pH can crash and cause significant damage.  However, if added with proper circulation and if the pH and TA are kept balanced, there's nothing wrong with using Trichlor, but of course those are big "if's".

As for Cal-Hypo, the increase in CH can cause scaling and that's more likely in spas due to the higher water temperature that increases the Calcite Saturation Index so it takes less CH, all else equal, to cause scaling compared to pools.  Unless one has very low CH with their fill water, then there's no reason to use Cal-Hypo and if one does use it then one has to monitor pH more carefully since it will tend to rise due to aeration of the water (see discussion of bleach below -- Cal-Hypo is also a hypochlorite source of chlorine so has the same issues one needs to consider, but it of course also increases CH which bleach does not).

Many of the recommendations from manufacturers come from rules of thumb assuming that spa and pool owners don't know what they are doing.  For example, most spa manufacturers or spa dealers say never to use bleach for sanitation.  In fact that is reasonable if one were to use ONLY bleach since the chlorine would then be too strong, but using Dichor initially or adding CYA at first will moderate chlorine's strength.  Also, using bleach without first lowering the TA significantly and using an alternate pH buffer such as 50 ppm Borates can have the pH rise too quickly and that can cause scaling (depending on the CH level).  So while the advice of not using bleach is sound for those who can't handle adjusting more than one or two things in a spa at a time, it's not absolute advice and there are many Dichlor-then-bleach users who have no trouble with their spas and get at least twice as much time between water changes.

[stuart]

Again, thanks....I've worked in the industry for over 30 years but have very little pool experience. In the last several years I've started writing a column in one "Hot Tub Only" trade magazine in the industry. This was a milestone to those of us that have felt like the red-headed stepchild of the pool industry.

Most of the chemical programs that we had came from the National Swimming Pool Institute and, having them right in my home town helps me research with them. The PHD that writes the brunt of the training, such as CPO certification, is a friend, neighbor and a spa customer of mine so it gives me a chance to work direct with him. Even he was surprised, when we installed an aftermarket generator and ph controller on his last spa, at how much corrosion occurred. We are about to install a different unit on his current spa late this month and experiment with it.

The big differences in chemical maintenance in a spa is that it's a much more volatile environment with the heat, turbulence and sheer bather load. Spas have a tendency to have a much larger gap between PH and TA.

I can tell you that what you see in pools, text books and lab testing will not be the same in a spa and often I bring things to the table that confuses or even astounds the pool industry top experts.

I also stay in constant contact with the Bio-Chemist that holds the patent on Di-Chlor for our industry and try to bounce things off her.

Having said all that, I can tell you that even the manufacture of bromine feeders have found tri-chlor and cal-hypo to be volatile to there spa units...I've helped them test them.

As a pool guy, cyanuric acid is part of your routine and something you're used to however many old time spa guys, real industry pros, never deal with it. Theory, pool water maintenance and even drinking water testing mean little to us as we aren't little pools!

The fact that you don't have a spa and aren't an industry pro makes your posts even more appreciated as you have nothing to gain here other then trying to impart knowledge. Thank you

[chem geek]

Thanks for the compliment and your insight.  One thing that is fairly constant between pools and spas is that industry folk in both don't really understand the chlorine/CYA chemistry.  They don't think there's any need for CYA in indoor pools or in spas not exposed to sunlight because they only think about CYA protecting chlorine from breakdown from sunlight and forget that it significantly moderates its strength.  That's a delicate balance because too low an FC/CYA ratio and algae can grow in pools (and even in spas if exposed to sunlight and not always kept hot).

So it's ironic that though some recognize that using Trichlor may build up CYA in pool, they don't think twice about using Dichlor in spas even though it increases CYA more quickly.  If they do realize it, they don't worry about it because the water can just be changed.  However, it does increase the risk of getting hot tub itch/rash/lung and the water can get dull/cloudy from chlorine not being able to oxidize bather waste quickly enough.

At the other extreme, you don't hear about any saltwater chlorine generator manufacturers talking about using CYA in the water for spas or indoor pools (they do recommend it for outdoor pools), yet the higher salt level will not only increase metal corrosion rates, but the full-strength chlorine with no CYA will also increase corrosion and be harsher on swimsuits, skin and hair, will outgas faster so degrade hot tub covers faster, etc.  There is hardly any research on this (unfortunately) but this study did find that "Moderate levels of Cyanuric Acid effectively inhibit corrosion caused by high chlorine levels".

[stuart]

You and I will differ greatly on a couple points however...

First, I will never recommend someone put bleach in their spa! I've seen it leave an ugly residue from other additives in the bleach and I've seen bad corrosion on spas from it. Funny, most pool guys I know are potentially ok with it however us old hot tub dinosaurs that have had to repair the damage time and time again in the field will always contradict that advice.

Second, I will turn everyone I can from trichlor or cal hypo in a portable spa no matter the reason you us it. I say portable spa because I've rarely seen the damage in the custom built in-ground units. This could be because they usually have a 1/4 of the plumbing or jets and usually have a feeder a long way away from the unit, plus they usually have at least double the body of water. Saying that however, I've replaced my fair share of heat exchangers from chemical damage over the years...

I know that theoretically there are several good arguments against my statements and even tons of forum groups that have so called experts spout statistics (usually biased towards what they sell) however, I would put my field experiences up against any of them!

[Topline Mike]

OK, Stuart, what sanitizer do you recommend in a portable spa?  I've been a spa operator for 3 days now!  I'm all ears. 

[stuart]

Mike, I'm using a salt generator...but then, like I said, I've replaced heaters and need to replace a pump seal. That's no big deal to me as I'm a tech and can do it pretty quick and I love the feel of the salt.

I'm not saying consumers shouldn't use salt, I'm saying it can be more corrosive and could even void warranty on some spas.

I've always been a fan of good old fashioned di-chlor...If you use it correctly it's hard to beat!

[swimspanevercame]

Any comments on the Gecko in.clear with bromicharge?  Is bromine less corrosive?  Thanks in advance for any knowledge in this area.

[Topline Mike]

So, did you use dichlor exclusively in your spa, or did you switch to chlorine once your CYA reached a certain level?  I heard you were a big fan of clorox bleach..   

[chem geek]

First, I will never recommend someone put bleach in their spa! I've seen it leave an ugly residue from other additives in the bleach and I've seen bad corrosion on spas from it. Funny, most pool guys I know are potentially ok with it however us old hot tub dinosaurs that have had to repair the damage time and time again in the field will always contradict that advice.

We're not talking about "experts" at forum groups.  We're talking about reports from real users.  Nearly 60,000 of them registered at just one pool forum, for example, with half a million visitors per month during the summer.  It's true that there are fewer spa forum users (across multiple forums).

As for bleach, I don't know what the people you are talking about have been using but one should not use bleach with additives -- do NOT use "splash-less", "outdoor", "fragrant", "heavy-duty", etc. since these additives do muck things up mostly causing foaming.  Regular unscented Clorox bleach and regular unscented off-brand Ultra bleaches do not have "additives".  There is a small amount of excess lye in bleach and chlorinating liquid while Clorox contains a very, very small amount of sodium polyacrylate.

Also, if such bleach users used bleach without adding any CYA in the water first, then as I already pointed out the corrosion rate WILL be higher because the chlorine is too strong since it is not moderated in strength if there is no CYA in the water.  The proper way to use bleach is to first add CYA in the water and the easiest way to do that in a spa is to use Dichlor initially until the CYA level builds up to 30-40 ppm (after roughly 33-44 ppm FC has been cumulatively added).

And as I also mentioned, when one switches to using bleach one needs to be very careful about preventing the pH from rising too quickly.  This is why one should significantly lower the TA level and use 50 ppm Borates when one switches to using bleach.  Otherwise one risks calcium carbonate scaling.

I don't dispute your experience, but I do question whether the bleach was used properly (i.e. the right kind and building up CYA first and having additional pH buffering).

I guess I'll have to tell the many dozens (maybe over a hundred; I haven't kept track) of spa users using the Dichlor-then-bleach method and reporting great results with no problems after nearly a decade that they will have to stop immediately because their spas are corroding horribly.  Or maybe not.

[Water Boy]

First, I will never recommend someone put bleach in their spa! I've seen it leave an ugly residue from other additives in the bleach and I've seen bad corrosion on spas from it. Funny, most pool guys I know are potentially ok with it however us old hot tub dinosaurs that have had to repair the damage time and time again in the field will always contradict that advice.

I guess I'll have to tell the many dozens (maybe over a hundred; I haven't kept track) of spa users using the Dichlor-then-bleach method and reporting great results with no problems after nearly a decade that they will have to stop immediately because their spas are corroding horribly.  Or maybe not.

Don't do that Chem geek. Your expertise for water chemistry speaks for itself, and I know I have learned a lot from you over the years, as has others. Just keep doing what you are doing. I know many have said they have used your bleach method over the years with great success. I personally don't use it or recommend it, but that doesn't mean I don't think it works either.

[chem geek]

I was being a bit facetious.  It's true though that the Dichlor-then-bleach method is certainly not for everyone because it is more complicated to set up and is riskier if you don't manage it properly.  Dichlor-only is very easy to explain and harder to screw up though even in that approach one can crash the pH and cause corrosion because Dichlor is net acidic when accounting for chlorine usage/consumption so the TA will drop over time, but such drop is slow and odds are that one gets close to doing a water change before the TA gets close to zero (and if one has evaporation and refill of water, then the TA gets brought up some to prevent it from crashing).  It would take around 280 ppm FC cumulatively added to exhaust 100 ppm TA and one would normally have to change the water in a heavily used spa using Dichlor about that same time, given the dull/cloudy water at that point.

Also note that I believe that the saltwater chlorine generators for spas can also be made to work much better with less corrosion if the same principles were applied there, namely if CYA were added to the water to reduce the active chlorine level as that should reduce corrosion.  Now the corrosion rate will still be higher than in a non-salt spa simply because the salt level increases corrosion rates, but it may be manageable for many spas that don't have low quality stainless steel or other components.  Again, the key is CYA because with no CYA in the water, the chlorine will be far too strong unless one keeps a very low FC level which is very impractical to do in a spa since the FC changes quickly due to the low water volume so relatively high bather load.  Also, the chlorine will outgas much faster with no CYA in the water so that depletes the FC faster and also degrades hot tub covers faster.

stuart is going off of his experience and as I noted it's perfectly valid and one should not question the validity of that experience if coming from a sufficiently large sample which I presume to be the case.  I just take a different approach to looking at experiences of spa and pool users to try and determine why the experience occurred and using science, when possible, to determine the root cause for what is seen.  That often lets one figure out what is really going on and sometimes lets one find a different approach that works well without the problems.

As an example, for many years TDS in pools was said to be the culprit for cloudy water and high chlorine demand or for getting repeated bouts of algae, but a scientific look at what is correlated with rising TDS shows that pools using stabilized chlorine have their CYA rise and the problem is not with TDS itself (which is mostly salt anyway) but with the higher CYA levels.  The science shows that the active chlorine level that prevents algae growth and oxidizes bathe waste is roughly proportional to the FC/CYA ratio so as the CYA level climbs if one doesn't proportionally raise the FC level then problems can start to occur.  The reason that algae doesn't always occur at low FC/CYA is due to other factors such as algae nutrient (phosphate, nitrate) levels.

As another related example, the pool industry touts that phosphate removal is necessary to prevent algae growth, but that is simply not true.  A sufficient FC/CYA ratio prevents algae growth regardless of algae nutrient level though the pool is certainly more "reactive" if you get lax and let the FC/CYA level drop so the phosphate remover should be seen more like an algaecide or as "insurance" if one doesn't think they can maintain an FC/CYA ratio.

There are many, many myths that have been disproven over time or shown to have different reasons for occurring than originally believed.  I absolutely believe that stuart saw corrosion in spas that used bleach.  The question is not whether that occurred, but why it occurred and what can be done to prevent it.  Though initially with the Dichlor-then-bleach method there was one user that got scaling because they didn't watch the pH and this was before I recommended using additional pH buffering of 50 ppm borates, since that time there haven't been problems from any Dichlor-then-bleach users without any reporting corrosion or other issues.  That doesn't mean the method is for everyone -- it's not -- but the method does work without side effects and with benefits of much longer time between water changes since there is no buildup of CYA that would otherwise reduce chlorine's effectiveness as with the Dichlor-only method.

[Topline Mike]

chem geek, it's obvious that you are truly passionate about water chemistry.  When I see you have made a post whether on this forum or on the others, I read it.  Thank you for all your help in the hot tub world.  I went from knowing absolutely nothing about hot tubs a month ago, to feeling pretty good about my water chemistry today. 

stuart, now you remind me of the Minnesota Vikings.  They've been playing football for a long time, and they still ain't worth a sh*t! 
Now that was a joke!  I am learning from all you guys with the years you have in the business.  Thank you. 

[stuart]

Chem Geek,
My comments were by no means meant to offend you...as I've said, you really have nothing to gain so your sharing of knowledge is greatly appreciated!

You've made my point much better then I did...many other systems are much harder to manage then dichlor and your way of using bleach may be effective but again, I would never recommend it to the average customer. I see people every day that still have their balancing agents from the start up kit in a box by their spa a year or more after delivery and yet they tell me "I check the water every week and it's always perfect. Then they don't understand when I tell them their pump seals have failed.

I would also agree with you on CYA, I'm currently testing the system out with borate to see if it lessens the corrosion. I would love to get the salt gen manufactures together with the chem experts and the field techs to see if we can't make it work more effectively!

Topline Mike...Wow...I think with the reputation I've earned over the last 30 years doing this I really don't have to low blows like that from anyone!

[Tman122]

stuart, now you remind me of the Minnesota Vikings.  They've been playing football for a long time, and they still ain't worth a sh*t! 

Hey!!!!! I take offense.