Please Advise Re: Water Chemistry For My New Hs Vanguard

[ht2020]

I finally pulled the trigger and purchased a Vanguard HS spa. The dealer asked me if I wanted "chlorine or bromine". I know nothing about either one of these options and was hoping that I could simply be told what to do ie: which one is best. I don't really want to become a spa water chemistry expert and was hoping that some knowledgeable forum members could simply direct me on this one. I do know that the Vanguard comes with a built-in Ozonater and a silver rod in one of its filters. I am willing to purchase whatever it takes to keep the spa clean and healthy. Any advice appreciated.

[chem geek]

If you are using the tub regularly, every day or two, and do not go away on travel away from the home frequently when no one will be around to maintain the tub, then chlorine should work well for you such as the Dichlor-then-bleach method. However, if you aren't using the tub frequently or won't be around to maintain it every day or two or at least twice a week, then bromine may be a better choice for you. The reason is that bromine can come in slow-dissolving tabs so can maintain the spa for you in between soaks. Also, with an ozonator and less frequent tub use, the ozone can make more bromine from an initial sodium bromide bank you initially establish while ozone and chlorine react with each other so if the tub is not used frequently then chlorine gets used up more quickly when an ozonator is also being used.

You can have the spa maintained using chlorine in between soaks if you use a saltwater chlorine generator such as the

'>ControlOMatic TechniChlor

.

[ht2020]

The hotsprings manual specifically says not to use bleach. Yet this is widely recommended in this forum. Why the discrepancy?

[PreservedSwine]

Because its easier to say, "Don't use household bleach," than it is to write another paragraph about the correct and incorrect types of bleach you can, and can't use.

[ht2020]

In the hotsprings manual they have a section in which they have bolded the word "DON'TS". Three of those items are routinely advocated in this forum eg: DON'T use household bleach; DON'T use muriatic acid to lower ph; DON'T broadcast or sprinkle the chemicals. I'm going to assume that the admonitions about bleach and muriatic acid are designed to have you purchase proprietary chemicals from the dealer or Hot Springs at 10X the price since it's obvious to me that many people on this forum have successfully ignored this.

[chem geek]

The admonition about not using bleach is due to several reasons. First is that if you use any hypochlorite source of chlorine without having any Cyanuric Acid (CYA) in the water first, then the active chlorine level will be too strong and harsh on equipment and hot tub covers as well as skin, swimsuits and hair and will also outgas faster so won't last as long. Second, is that at normally recommended Total Alkalinity (TA) levels from the manufacturers, carbon dioxide will outgas causing the pH to rise (when using hypochlorite sources of chlorine) and this can cause calcium carbonate scaling depending on the Calcium Hardness (CH) level.

This is why when using bleach the method has one add CYA first, usually by using Dichlor initially to build up CYA. This is also why we have the TA level be significantly lowered to 50 ppm and add 50 ppm borates as an additional pH buffer. Obviously, this is more complicated than just adding a single chemical to start off so is why manufacturers don't recommend it. Finally, most do not understand the FC/CYA relationship. As to whether hot tub manufacturers are trying to help dealers sell more chemicals, that's possible but not likely since the manufacturers don't generally get any revenue from the chemical sales if the chemicals are standard products such as Dichlor for which there are multiple brands.

As for Muriatic Acid, it's a harsh chemical and if you add it too quickly to the water without circulation, it can pool at the bottom of the spa since it is denser than water (until mixed) and damage surfaces. However, if added slowly with circulation, there should be no problem using it though it can fume (lower concentrations of 15-16% fume less than full-strength at 31.45%).

[ht2020]

Very cogent explanation about the dichlor then bleach method. It's slightly more involved but may be worth the effort if I don't need to change the water as often. How can you "prove" that this method reduces water changes by 50%? I don't mean to be super-geeky about it but what parameters do you use that indicates when the water has to be changed, and are those parameters demonstrably better when you do the dichlor then bleach method? I realize that CYA can be tested with strips and that the dichlor-then-bleach method would have a better chance of controlling residual CYA than the conventional methods, but does lowering this residual CYA necessarily reduce the frequency of water changes. Also, with regards to your point about muriatic acid: I assume that you could avoid sedimentation by dissolving it in a container of water before adding it to the spa?

Last point: I fully understand that Hot Springs/Watkins has no great vested interest in selling their own products but I feel that they probably have a vested interest in supporting their dealers. Their dealers are counting on a lifetime of customer purchases of these products (whether or not the products are proprietary to Hot Springs) and would probably be significantly irritated if Hot Springs were to recommend buying bleach and muriatic acid from Home Depot (for 10-20X less cost than the branded stuff).

[chem geek]

The time between water changes is what is reported by users of Dichlor-only vs. Dichlor-then-bleach, usually the same users who started with the former and then switched to the latter. They report that using Dichlor-then-bleach not only can they go longer between water changes, but that the water isn't in bad shape when they do change it. With Dichlor-only, they notice a dramatic improvement in the water (mostly clarity) when they change the water, but with Dichlor-then-bleach the change is less dramatic because the clarity is better when the water does get changed. It gets changed with Dichlor-then-bleach because the chlorine demand increases from very slow-to-oxidize organics and because the salt level builds up. Hopefully some of them should report in (or you can search posts on this forum) since you shouldn't believe what any one person tells you on the Internet.

Technically the reason the water lasts longer is that with Dichlor-then-bleach the CYA level doesn't build up so the active chlorine level remains consistent so the rate of oxidation of bather waste remains consistent. With Dichlor-only, the CYA builds up and is readily measured (with a proper test kit), the active chlorine level drops as a result, and bather waste builds up making the water dull/cloudy and sometimes smelling sooner. The disinfection level also drops and may explain some of the hot tub rash/itch/lung incidents, some of which occurred after months of Dichlor-only usage, though the sample size is way too small to be definitive about that.

The science of the chlorine/CYA relationship has been known for a long time and the equilibrium constants definitively determined in 1974 in this paper.

As for testing CYA, don't use test strips since they are pretty awful. Use the Taylor K-2006 test kit.

As for pre-diluting the Muriatic Acid, yes that would help if you diluted it enough, but really it's just about decent mixing and one can readily add it slowly with the circulation pump running and do fine.

You make a valid point about Hot Springs/Watkins wanting to support their dealers and that the dealers want recurring revenue from chemical sales. The pool/spa chemical industry is well over a billion dollars so certainly has an incentive to promote the more profitable higher margin products compared to identical household alternatives.

[ht2020]

I am currently using a hybrid system ie: daily MPS before the soak (1 oz) followed by 0.5 oz dichlor after the soak. THere is a freshwater silver sanitizing stick in the filter. I am assuming that since I am using a "low-chlorine" method there will be less CYA accumulation? In fact, would this kind of method even justify the dichlor then bleach method?

[chem geek]

MPS is far more expensive than bleach. The whole purpose of using the silver ions with MPS is to not use chlorine, at least most of the time. The hybrid approach doesn't make much sense. You either want chlorine or you don't. You either want to spend more money to avoid chlorine or you don't and are willing to use chlorine.