Tips
on selecting, installing and maintaining UV systems in commercial pools
The prevalence of UV water treatment is
growing in commercial pool applications throughout the U.S.
Installing a UV-C system at a
commercial aquatics facility will lower chemical usage by up to 30- to 50
percent and achieve safer water by eliminating pathogens, viruses and
chloramines. In addition, the reduced chloramines will improve the air quality
around the pool, especially for indoor facilities. This article will cover the
selection of UV-C systems, as well as their installation and maintenance.
Getting started
UV sanitizers offer plenty of unique benefits. However, there are different types, and the proper unit should be selected for specific aquatics applications. In particular, it is important to match the unit size to the pool or waterfeature type — for example, splashpad, play structure, lazy river, etc. Pool professionals who understand the differences can easily determine which unit to recommend.
UV sanitizers offer plenty of unique benefits. However, there are different types, and the proper unit should be selected for specific aquatics applications. In particular, it is important to match the unit size to the pool or waterfeature type — for example, splashpad, play structure, lazy river, etc. Pool professionals who understand the differences can easily determine which unit to recommend.
There are two types of UV lamps. First,
there are low-pressure, high-output lamps, which emit UV rays at 254
nanometers. On the other hand, medium-pressure lamps emit UV rays between 200-
and 600 nm.
Low-pressure lamps are better suited
for semicommercial and commercial applications with lower flow rates and light
bather loads, while medium-pressure models are designed for large commercial
installations with high flow rates and heavy bather loads. The differences
between each lamp are cost, flow requirements and the ability to destroy
chloramines (NH2Cl).
Medium-pressure lamps are commonly used
for indoor pool applications because their large light spectral is more
effective at reducing the health problems caused by nitrogen trichloride (i.e.,
chloramines), which have been linked to numerous pool closures due to poor
indoor air quality.
For semicommercial applications such as
hotels, motels or fitness facilities with flow rates more than 110 gallons per
minute, a low-pressure, high-output UV system, or an amalgam unit designed to
accommodate higher flow rates should be considered.
Selecting a UV-C sanitizer
UV-C systems are sized according to the gallons per minute generated through the filtration system, not the volume of water in the vessel. Bigger is not always better here. The gpm rating is based on lamp and vessel design along with a computational fluid dynamic computer simulation. The correct power rating for a commercial UV unit is 40 megajoules, based on the NSF/ANSI 50 standard. That is the point at which it will sterilize all pathogens found in pool water.
UV-C systems are sized according to the gallons per minute generated through the filtration system, not the volume of water in the vessel. Bigger is not always better here. The gpm rating is based on lamp and vessel design along with a computational fluid dynamic computer simulation. The correct power rating for a commercial UV unit is 40 megajoules, based on the NSF/ANSI 50 standard. That is the point at which it will sterilize all pathogens found in pool water.
A UV-C unit will handle a range of
flows. Manufacturers will produce each unit for a minimum and maximum flow in
gpm. As an example, unit XYZ will handle 57 to 80 gpm. If the pool system’s
flow rate exceeds the UV-C unit’s maximum gpm rating, the sanitizer cannot
achieve the intended 99.9 percent single-organism sterilization. If the water
flows through the UV vessel too quickly, the contact between the water column
and the UV-C light in the chamber is not long enough to achieve sterilization.
Conversely, if the pool water flows too
slowly, it stays in the light chamber too long, and some free chlorine
photo-oxidation will occur, thereby increasing the amount of chlorine needed in
the pool to achieve enough free chlorine residual.
All of the sterilization happens within
the vessel, and UV-C does not leave a residual or create any corrosive gas.
Another factor that should be considered when selecting a UV-C unit will be
lamp life. UV-C lamps are rated in hours of service life, which is the period
of time during which the lamp will produce enough millijoules of UV-C power to
properly sanitize the single-cell organisms in the water. Lamp life typically
ranges from 6,000 to 16,000 hours, which, in real-world terms, means there are
lamps that have a 12-, 16- or 24-month service life. It’s beneficial to
purchase a unit that is NSF 50 certified because many municipalities require
this.
Installation procedures
UV-C units should be installed in line in the plumbing.
UV-C units should be installed in line in the plumbing.
UV-C units must be placed after the
filter, and particulate in the water can create a shadow effect inside the
unit, between the lamp and any single-cell organism we are trying to sterilize.
If there is a heater in the system, the
preferred location for the UV-C unit is before the heater. Using a UV-C unit
will extend the life of the heater by removing chloramines, which are
corrosive to the metal in the heat exchanger. Some equipment pads are tight, so
if the UV-C unit must be installed after the heater, check with the
manufacturer to ensure that the plastic used in that particular unit will
handle hot water coming out of the heater.
The units should be installed with
enough room for technicians or operators to perform lamp replacements and
quartz-tube cleanings in the future. The glass lamp and quartz tubes cannot be
bent, so it is important that there be enough space to remove them straight out
of the UV system.
A typical pool with a UV-C unit also
will include a chlorine feeder. This should be plumbed after the UV-C unit,
typically last in line before the water returns to the pool.
UV systems can be easily added to an existing circulation system — again, after the filter and before other accessories such as heaters or chlorinators.
UV systems can be easily added to an existing circulation system — again, after the filter and before other accessories such as heaters or chlorinators.
The unit should be plumbed in according
to the manufacturer’s instructions so the UV system properly fills with water
in relation to the unit’s flow rating.
Many professionals
plumb in a bypass. This makes servicing and maintenance easier by allowing the
operator or technician to separate the UV system when necessary, especially
during winterization. Because the UV lamp and quartz tube are made of glass,
they must be brought inside to avoid winter damage, such as freezing, when the
pool is not being used. This applies to outdoor commercial pools that might
close in the winter.
As found on Aquatics
International:
