Using plain ol' salt in wood tub as sanitizer. Why not?

[Dr. Spa™ Ret.]

Ozone wont work, and will quickly deteriorate the wood.

Ozone, while a very powerful oxidizer, is only so, when it's ABSORBED into the water. In order for it to be absorbed into the water it has to have a long contact time with the water, and the water has to be pressurized. Ideally the contact time is 25+ seconds, and the water would be pressurized to at least two atmospheres. In your situation, the contact time would be about 1 second, and the water not pressurized at all. The ozone would bubble to the surface of the water, and being heavier than air would accumulate in VERY high concentrations, and deteriorate the wood above the water line. I saw a wooden hot tub, 3 years old, with this setup, and the wood above the water line had lost 1/2+" of thickness.

[fishnaked]

Ozone wont work, and will quickly deteriorate the wood.

Ozone, while a very powerful oxidizer, is only so, when it's ABSORBED into the water. In order for it to be absorbed into the water it has to have a long contact time with the water, and the water has to be pressurized. Ideally the contact time is 25+ seconds, and the water would be pressurized to at least two atmospheres. In your situation, the contact time would be about 1 second, and the water not pressurized at all. The ozone would bubble to the surface of the water, and being heavier than air would accumulate in VERY high concentrations, and deteriorate the wood above the water line. I saw a wooden hot tub, 3 years old, with this setup, and the wood above the water line had lost 1/2+" of thickness.

Thanks. That's good info to have! The "contact time" was one of the issues I now remember reading about too.

How about UV light? I believe it's expensive and requires that the water be circulated (ie, I'd have to buy a pump = even more $) to be effective. Any other thoughts on that?

Seems there are a lot of inquiries on the Net from folks who don't want to use the standard chemicals but I see few solid solutions. Surely there's something that would actually work. Maybe my expectations are too high. I must say though that dumping ~1/2 cup of 35% peroxide in my tub after each soak works considerably better that the cup/wk I was doing prior. Still though, it's a far cry from what some people are claiming as I'm still seeing some moss 30 days in...and I'm concerned that the peroxide might damage the powder coating on my Snorkel stove.

The Ahhnatural tea bag-like thing looks some what intriguing but it calculates out to be $25/month...or perhaps as little as $16 if one can squeeze 18 months from it like it is claimed some do. What's in the thing though!!??.

EDIT: Just to be clear, I do not expect to keep water in my tub 1 year before changing. I'd be happy to get 4 months between changes. Heck, 3 months wouldn't even be bad.

[chem geek]

If you are talking about moss on the wood, then a UV system won't help at all because it only kills what circulates through it.  You need a disinfectant in the bulk water.  You've already been told how you can use chlorine in the spa in a way that you would not notice the chlorine (i.e. dose after a soak such that you start your next soak with hardly any chlorine).

Moss can be killed effectively by copper ions, just as algae is prevented as well.  So a copper/silver/zinc system would work and you could use non-chlorine shock (potassium monopersulfate, MPS) to oxidize the bather waste.  The combination of silver ions and MPS is also an EPA-approved disinfectant (technically only in the Nature² system since the EPA approves products, not chemicals).  I don't know, however, if there are any problems with using metal ions in a wood spa.

[Dr. Spa™ Ret.]

No problem with metal ions in a wood spa...however, he has no pump, filter or circulation system of any kind.

[fishnaked]

Moss can be killed effectively by copper ions, just as algae is prevented as well.  So a copper/silver/zinc system would work and you could use non-chlorine shock (potassium monopersulfate, MPS) to oxidize the bather waste.  The combination of silver ions and MPS is also an EPA-approved disinfectant (technically only in the Nature² system since the EPA approves products, not chemicals).  I don't know, however, if there are any problems with using metal ions in a wood spa.

Thanks. Couple questions:

What is MPS? What about the peroxide I am using for a shock?

Re the EPA, who approves chemicals then?

[fishnaked]

No problem with metal ions in a wood spa...however, he has no pump, filter or circulation system of any kind.

Thanks. Does that mean the metal ions would not work, or not work as well as they could, without the pump and filter?

[chem geek]

The metal ions would work as well as anything else you'd add to the tub.  Basically, ANY chemical you add to the tub would need to get mixed in the water somehow.  Once mixed, it should stay mixed.  The metal ions are mostly just dosed after you do a water change since they mostly last.

MPS is non-chlorine shock (potassium monopersulfate).  It oxidizes bather waste and would be added after each soak, but you'd need to stir the water to mix it.

With no filter and circulation, your spa will build up dead skin cells and other organic material since oxidizer products do not completely get rid of them.  The only way to clean out your spa effectively of such items will be with water replacement.