Do UV Ozone Pool Systems Really Work?

[piazzadesign]

Hey all,

I'm about to sign a contract to have an inground pool and spa built at my home in southern California. This will be my first pool. The contractor that we're leaning towards going with swears by what he describes as a "UV Ozone" system and claims it's far better than a salt system and that he puts them in 90% of the pools he builds. However, another contractor that we also like tells us that the UV Ozone systems are "snake oil" and they don't work at all. He says that pools that use those systems are totally reliant on the added chlorine to stay clean and that often when the uv/ozone system fails the owners don't even notice because the chlorine is doing all the work. I've been searching for reviews and comparisons of the two types of systems, but I've found nothing that gives a straight answer or that isn't marketing material for companies that make or sell the systems. Can anyone shed some real light on this subject for me? 

[RDspaguy]

I sure can. I am a BIG fan of ozone, and uv as well to a lesser extent, IN SPAS. Spas have a small water volume and high turnover (the time it takes for the entire volume to be circulated) and spend 90% of the time covered, so no (or few) new pathogens are entering the water when not in use. This means that you don't need to maintain a residual (constant level of sanitizer in the water). Pools are another story.

Ozone is an oxidizer (think shock), one of the strongest known, and will burn off both fc (free chlorine) and cc (combined chlorine, think "used chlorine") in the water. It eliminates chlorine, but DOES NOT eliminate the NEED for chlorine in the water. It is a sanitizer, in that it destroys pathogens it contacts, but it only treats a small portion of the water (what is in the pipe) and returns that clean water to a pool full of multiplying pathogens. Therefore, it cannot keep your pool or spa sanitary by itself. It does not establish a residual in the water, but dissipates within seconds.

Uv also destroys chlorine. This is why you use cya (stabilizer) in a pool, to stop uv dissipation from the sunlight. As the uv energy of a uv purifier is much stronger than sunlight, it will dissipate stabilized chlorine as well.

Since a pool is open at all times and gets new pathogens added every time the wind blows, you must maintain a chemical residual in the water or you will have trouble. As both ozone and uv ELIMINATE your residual, they are a bad idea in a pool, unless perhaps it has an automated cover and is closed 90% of the time.

So, in short, you use ozone and uv to eliminate unwanted chemical residuals from your spa, but you need those chemical residuals in your pool.

Salt systems are chlorine generators, splitting the salt (sodium chloride) molecule into it's base components of sodium and chlorine. As they produce a locally high chlorine level at the generator, they also shock (oxidize) the water to an extent. The chlorine produced is very high ph and will require more frequent adjustments or ph automation to avoid scale, which will plug up the salt cell as well as cause other issues in your pool and equipment. While really no more hands on maintenance than any other chlorine system, swg (salt water generators) are expensive and self-destructive if you get lazy about maintenance. 

I personally prefer chemical automation. Peristaltic pumps controlled by a electronic system that tests the water every 15 minutes and pumps in liquid chlorine and acid from buckets as needed. A bit more $ at install, but very little $ to maintain, and very little hands-on chemical additions. This is what most public pools use. All you have to do is keep the buckets full and properly store the probes at closing time.

[piazzadesign]

Thanks for that info. We've already decided that we will definitely not go with a standard chlorine pool (auto-fed or otherwise). My wife has very sensitive skin and we've found that the salt system pools at houses we've rented are much better on her skin than the standard chlorine ones. UV/Ozone "sounds" like a possible alternative, but I just have yet to find even one single person who has a UV/Ozone pool to offer their opinion of it. I guess that really should tell me all I need to know, but I want to do as much due diligence as possible.

[RDspaguy]

Well, a salt system, as I described, is a chlorine generator. It is still a chlorine pool and is still treated like one, including shocking with chlorine as needed. Don't get me wrong, there are many happy swg users out there, and if you do a good job with balancing your water you can get several years out of that $800 salt cell. But if you get lazy about it you can go through 2 a year.