Swimming Pool Tip #48: Ozone Pool Sanitation Problems

Ozone Swimming Pool Sanitation: Full of Gas?

You may have heard of sanitizing swimming pools with ozone . . .

Ozone is a great swimming pool oxidizer (destroys trash) and sanitizer (kills little 'beasties'). And, ozone is reported to be an environmentally friendly alternative to chlorine. In fact, ozone does almost everything chlorine does, and everything it does do, it does better than chlorine (really, it does)!

So, you should run right out and get an ozone system for swimming pools, right? Maybe not.

Well, there are a few little things you should consider, first. Ozone doesn't kill algae, but you could work around that.

Some ozone delivery systems tend to eat up alkalinity in your pool, which in turn, eats up swimming pool plaster. Still, if you keep testing and adding baking soda every few days, you could avoid damage.

Of course, you'd have keep in mind that good swimming pool ozone systems are expensive to buy, and to maintain. Even UV based systems need frequent replacement of expensive mercury (talk about environmental hazards!) lamps. But, with your income, you don't mind a little more expense, do you?

But there's one small problem left. It's the problem of where ozone is, and where it isn't.

And where ozone isn't, is in your swimming pool!

No, no misprint.

Swimming pool ozone systems do NOT ozonate the water in your pool! They only ozonate the water in your pipes: they are DESIGNED to assure that no ozone ever reaches your swimming pool, and the swimmers in it. (Some systems only ozonate the water in a portion of your pipes!)

The reason is simple: ozone is poisonous, not just to bacteria, but also to people! So the bottom line is this: to protect your safety, all swimming pool ozonation systems are designed to assure that no ozone reaches the pool.

Nada. Zip. None at all. Not even a little bit.

In fact, the safety secret of many US residential ozonators is that they produce so little OZONE that there's never any danger! (I just call them 'lowzone' systems!) European pool ozonators require a complex systems of tanks to hold the ozonated water for a few minutes, and then more tanks and filters to take the ozone back out, before it can reach the pool, and hurt the swimmers! These very elaborate and very expensive systems do in fact produce very high water quality. The US 'lowzone' systems? Well. . . I wouldn't buy one!

[Actually, I bought two, a number of years ago. One is still installed on a customer's spa, but not running. I never billed for it, either! The other is RIP in a back corner of my shop.]

Still, the ozone cleans up the water in the pipes, and all the water in your pool goes through the pipes every 8 hours, right? Well, not quite.

Under ideal circumstances, in well designed home swimming pools, an amount of water equivalent to the volume of your pool passes through the filter every 8 hours. But (and this is a big "but") because of hydraulic short circuiting, it typically will take 3 to 4 days before 99% of your swimming pool's water has been filtered and ozonated!

But, in the real world, many swimming pools turn over their water only every 12 hours of pump operation, but, they only operate their pool, 6 - 8 hours per day.

Under ideal circumstances, in an ozonated swimming pool, it takes 3 to 4 days before most of the critters, bugs and beasties found in the leftovers from Johnny's runny nose, have to run the ozone gauntlet. But in many typical pools, it will take weeks before ozone gets a chance to kill these pathogens. And that's a problem -- unless you don't mind sharing Johnny's cold with everyone else who swims during that period.

So all ozone santation system manuals tell you -- in the fine print somewhere -- must still add chlorine or bromine to your pool. Why? So there's something in the pool water (not just in the pipe water!) to kill germs where the swimmers are.

When you chlorinate the pool, chlorine is not only in the pipes, but also in the pool, where it can keep the virus making Johnny miserable from making the rest of your family miserable, too.

Guess what? A lot of US ozone makers know that their ozonation systems don't do much. So, they recommend using of chlorine, to help the ozone. Unfortunately, this is a bit adding water and wood to your fire -- at the same time! Why? Well it works like this:

Fortunately, most ozone systems sold in the US put out so little ozone, that they don't use up much of the chlorine. Using one of these system, your chemical costs will only be slightly higher with the ozonator turned on, than with it turned off!

If your dealer says it ain't so, here's just one reference:  pgs. 898-902, White, Geo. Clifford The Handbook of Chlorination, 2nd ed. (New York: Van Nostrand Reinhold Co. 1986)

Ozone's neat stuff, but not real practical for residential swimming pools. Ozone systems can perform reasonably well in spas, which turn over an equivalent volume in as little as 10 minutes. And pool ozone systems are really good at performing wallet-ectomies, if you are in need of one!

Note, 4/99 
I have received some credible reports of homeowners achieving very good results on their pools, using corona discharge ozone sytems combined with very low levels of chlorine and stabilizer. One pool serviceman, in whom I have considerable confidence, reports using such a system on his own pool . . . and has promised to write a page for me, describing his system, and its results. Until he does, I can't give you any details, because I don't have them. He readily acknowledges, though, that many of the pool ozone systems he has seen, perform as poorly and the information above suggets. Also, one of my website subscribers has a Laars 'Maxx-Pure' system, no longer available, with which he is quite pleased.

Unfortunately, neither case has provided me with information on a 'recommended' ozone system, for folks who really want one.

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Want to check it out for yourself? Try the following:

Langlais, B. et. al. Ozone in Water Treatment: Application and Engineering (Lewis Publishers 1991)
Rice, R. G. ed. Ozone Treatment of Waters for Swimming Pools (Vienna, VA: The International Ozone Association 1982)
White, Geo. Clifford The Handbook of Chlorination, 2nd ed. (New York: Van Nostrand Reinhold Co. 1986)

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