There are two concerns with keeping swimming pools clear and healthy for bathers.
The first is a sanitizer - something to kill germs and bacteria. What ever is used, it must remain present in the water 24 hours a day, every day. There must be enough already in the water or available for injection to handle spikes in temperature and bather loads.
The second is something to function as an algaecide. The most effective algaecides are heavy metal ions such as nickle, copper and silver. In microscopic doses, they work well and are safe for the environment. However, there is no easy means to measure the levels of these metals.
There are a number of ways to get heavy metals into your pool water.
Pouring in an algaecide that contains these metal compounds is the fastest. There are many on the market. However, they result in a large dose of metals.
Erosion ionizers are cartridges that contain heavy metal compounds that gradually emit metals into the water as the water passes through them. Cartridge balls can be placed in the skimmers or pump baskets, or in-line cartridge dispensers can be plumbed into the pipes (like an oil filter).
Active ionizers are electronic devices that use electricity to emit metal ions into the pool water. These are always plumbed into the pipes at the equipment pad.
Contrary to manufacturer's claims, metal ions do very little to kill bacteria and germs. They work so slowly on killing germs and bacteria, they are only relied upon to keep algae and plant life at bay.
Ozone is the best form of germ and bacteria killer used in swimming pools. Ozone also breaks down contaminates that bathers introduce into the water - fabric softeners, cosmetics, suntan lotions, soap and shampoo residues, etc.
A properly sized ozone side stream system can cost $10,000. As the size of the pool increases, the cost rises exponentially, as they are sized to match the size of the pool and the bather load.
Ozone is gas that is very reactive and therefore has a very short half life. Because it does not last, it cannot be bottled and must be manufactured on site.
Ozone is thousands of times more effective at killing microorganisms that chlorine. Due to it's short half life, ozone only remains in the water while it is actively being produced. Shut off the ozone generator and within minutes, the ozone in the water is gone.
Ultraviolet Light (UV)
Ultraviolet light kills germs and microbes using the radiation that exists in UV light. It does not emit any residual sanitizer into the water.
Because it requires a light source, a device is plumbed at the equipment pad. The water passing through the device is exposed to the UV light, killing the organisms. The pumps must be operating for the UV lamps to operate. And only that amount of water that can pass by the lamps is treated.
Truly Chlorine Free
To truly achieve a chlorine free pool requires that an OVER SIZED corona discharge ozone system be ran 24/7. If complemented by a UV system, a chlorine free pool could be achieved.
But it requires that the circulation pump be operated 24 hours a day, everyday. And it has associated costs - the equipment, maintenance and electricity.
Ultra-Low Chlorine Pool
By contrast, one could operate a properly sized ozone system with UV for 6-8 hours per day... provided that they maintained a very low level of chlorine.
That chlorine level could be so low, say 0.5 ppm (parts per million) and still maintain clear sanitized water. To keep the chlorine precisely at such low levels would require an ORP/pH controller to micro-dose the chlorine. As demands increased or decreased, the controller would adjust it's output to maintain 0.5 ppm.
0.5 ppm of chlorine is approximately the level in found in drinking water.
Safe for human consumption and even for watering plants!
Paolo Benedetti, SWD, Principal
Aquatic Technology Pool and Spa
International Swimming Pool Consulting and Design, Aquatic Consulting, Watershape Consultants, Expert Witness, Hydraulic Design, Landscape Architecture, Construction Management
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