Need Information On Methods For Chemistry Treatmentm- Uv? Silver? Cl? ...

[awolf]

I am still shopping. While I am at it, I have heard many different approaches for how to maintain germ-free operations with everything from daily Cl treatment to Br floaters to silver catalysts to Ozone to UV. Is there a thread here that compares the methods on effectiveness AND operating costs to help me understand what I am in for. Is it brand dependent e.g. will D1 be different than Hot Springs or Sundance? Thanks

[chem geek]

Forget the UV. As for ozone, it is helpful if you use the spa a lot, at least every day or two, since it can oxidize bather waste so you use less oxidizer (chlorine or bromine), but it cannot be used alone. If you don't use the spa much and want to use chlorine, then I'd go without the ozonator since it would just needlessly increase chlorine demand. If you don't use the spa much and don't want to dose every day or two, then you can use the 3-step bromine method which can maintain bromine levels using bromine tabs, but some people don't like the smell of bromine/bromamines. There's also saltwater chlorine generator products (ControlOMatic TechniChlor, Hot Springs® ACE® saltwater sanitizing system, etc.). If you don't want to use much chlorine/bromine, then Nature2 silver ions with MPS is an option, though you'll still need to use chlorine once in a while (perhaps once a week or so).

The least expensive approach is the Dichlor-then-bleach method, but requires more maintenance which isn't a problem if you're using the spa every day or two, but can be annoying to some for spas not used frequently. Next would probably be Bromine tabs using bleach to oxidize. The saltwater chlorine generator is more expensive up-front, but then doesn't cost much afterwards. Nature2 with MPS is expensive ongoing.

Without an ozonator, one person-hour of soaking requires around 3-1/2 teaspoons of Dichlor (27 cents), 5 fluid ounces of 6% bleach (10 cents), or 7 teaspoons of non-chlorine shock (43% MPS) (52 cents).

None of these methods depends on the brand of hot tub (except the specific Hot Springs® ACE® chlorine generator system). All of the above are sanitary and EPA-approved disinfectant methods.

[awolf]

Thanks! Since I live in an area that will have snow in the winter, can I add the 'daily' Cl before getting in? Or would I need to go back out and add it after soaking (less desireable to go back out then ....)

I need to go read up on why the Ozonator increases Cl demand. Must facilitate some reaction that scavanges Cl- ions?

Also, The D1 salesman says I need their system, which is a weekly treatment, but it costs $150 for about 5 months of supply. I need to understand what the product is. (any help there?)

[Dr. Spa]

Go back out? Why wouldn't you bring it with you and put it in as you get out?

Ozone destroys chlorine (and chlorine destroys ozone).

[chem geek]

As Dr. Spa says, you can just take the chlorine with you and add it right after your soak. Actually, you'd take your test kit with you as well and test before your soak, at least until you understand your pattern of usage better. Test before, add oxidizer afterwards. That's the key. Add enough oxidizer (usually chlorine, if doing this every day) so that you have some small measurable amount before your next soak (say 1-2 ppm FC) assuming you want to minimize chlorine/chloramine smell during your soak.

As for the D1, are you talking about their Vision cartridge? That's a silver ionizer, similar to Nature2. However, I don't believe they got EPA approval for use with MPS (not sure why -- maybe cost or maybe they don't control the silver release very well) so if you need to use chlorine anyway, then there's no need for the cartridge, especially if you are diligent about dosing with chlorine every day. Do NOT follow their recommendations for TA which they say should be 125-150 ppm or else your pH will rise too high. The TA should be lower, especially if you use the Dichlor-then-bleach method. Read Dichlor/bleach Method In A Nutshell (though I recommend you use the 50 ppm Borates -- I don't consider this optional unless you have virtually no aeration in your spa). The main advantage of the Dichlor-then-bleach method, in addition to its low cost, is that it should let you be able to go at least twice as long between water changes.

The reaction of ozone with chlorine (and with bromine) is described in Chemistries of Ozone for Municipal Pool and Spa Water Treatment and more specifically in Kinetics and products of the Reactions of Ozone with Various forms of Chlorine and Bromine in Water. The result is 77% chloride ion and 23% chlorate ion (and oxygen gas in both cases). So when there is high bather load, then ozone can oxidize it reducing the amount of chlorine needed to do so, but when there is little or no bather load then the ozone just ends up using more chlorine by reacting with it. So if you are going to use the tub for every day, especially if for a longer time or with more than one person, it may be worth getting an ozonator, though is not essential.

[awolf]

Thanks for the links! Do I understand that using the Silvier Ionizer that many dealers promote is NOT an option with D1? Or just not their Vision Cartridge?