Ultraviolet Pool Systems
The power of the sun to kill bacteria has been known to man for millennia. This is why moss grows on the shady side of trees, and why mold prefers dark spaces. It is, the UV or ultraviolet rays of the sun that target the DNA and RNA of microorganisms, ripping apart their cellular structure. UV acts as a photo-oxidant by the use of photolysis.
UV-C is a short wavelength ray within the spectrum of UV light between 200 and 280 nanometers, which is the most effective range for disinfection and sanitation purposes.
UV pool systems use a special UV lamp which emits a UV-C germicidal ray, which is effective against algae, bacteria, viruses, parasites and protozoa, and even removes chloramines. The UV lamp is housed in a chamber which is protected from the water by a hard quartz sleeve; as the water passes through the chamber, at a specific flow rate, up to 99% of contaminants are eliminated.
Ultraviolet pool systems are not considered a stand-alone product, because of a limited lifespan. Like Ozone, another popular supplemental sanitizer, UV rays do their job in just seconds, and outside of the purification chamber, or ozone injection point, the water is unprotected. Because the water is only purified as it passes through the UV chamber, Ultraviolet pool systems are normally used with a low amount of chlorine, in the range of 0.3 – 0.8 ppm, to protect the water during the other 99% of the time that it is not flowing through the chamber.
Ultraviolet pool systems are made by Del, Delta, Fluidra, Pentair, Solaxx. They are installed after the filter and heater, and before any chlorine or ozone units.
UV Systems and Salt Systems
UV is compatible with pools using a salt water chlorine generator. If adding an Ultraviolet pool system to a salt water pool, be sure to use one that has a chamber that won’t be affected by salt water.
Maintenance on Ultraviolet Pool Systems
Most UV lamps have a listed lifespan of at least 10,000 hours. Most manufacturers recommend replacing the UV bulb annually, but for a seasonal pool, you may be able to operate for more than one season before changing the bulb. Most UV systems also need an annual cleaning of the quartz glass shield, which involves removing the shield and submerging in an acid solution for a few minutes and wiping clean. Many systems also have a small screen or filter that need to be cleaned once or twice per season.
Maximum Flow Rates for UV Systems
Every UV system will list a maximum flow rate. For the UV to have time to sanitize, the water can’t be forced through the chamber too quickly. Ideally, a UV pool system installation will entail a measurement or evaluation of the system flow rate. If the current flow rate in the return line exceeds the UV system design flow rate, a bypass can be plumbed into the system. The drawback to this is that you will be purifying less of the water, unless you install two UV systems, in parallel.
Turning On/Off the Bulb Shortens the Life
The UV-C bulb is meant to be on all the time, but it can’t be operating unless there is water flowing through it, so most systems utilize a pressure switch to shut off the lamp when the pool pump shuts off. Many manufacturers of UV pool systems say that a daily on/off cycle won’t have much effect, but that one should avoid multiple daily on/off pump cycles, to extend the lifespan of the UV-C bulb.
Don’t Touch the Bulb, Don’t Even Look at It!
The UV-C bub, like other bulbs that burn hot, such as halogen bulbs, can develop hot spots if the oil from your fingers gets on the bulb. Always handle with soft gloves or a cloth. Don’t look at the bulb either, while it’s burning, that is. Most systems are sealed to prevent eye damage which could result from staring into a UV-C bulb.