In practice, low pressure and medium pressure UV-C systems are often compared as competing technologies. However, that is not entirely accurate. Both technologies serve the same core purpose — disinfection — but they differ fundamentally in operation and effect.
To make the right choice, it is important not only to look at the technology itself, but especially at what is happening in the pool water.
Two Technologies, Different Impact on Water Quality
The main difference between low pressure and medium pressure UV-C lies in the type of radiation that is produced.
Low pressure UV-C lamps operate with a narrow, focused wavelength around 254 nm. This is exactly the point where DNA is most sensitive to UV radiation, making these systems highly efficient for disinfection.
Medium pressure UV-C lamps, on the other hand, produce a broad, polychromatic spectrum. As a result, not only DNA is affected, but also other cell structures such as enzymes and cell membranes.
While this difference may sound technical, it has a direct impact in practice.
What Can Low Pressure UV-C Systems Do — and What Can’t They Do?
Low pressure systems are optimized for efficient and stable disinfection. Thanks to their high efficiency and low energy density, they are particularly suitable for applications where reliability and low operational costs are key.
In swimming pools, this means that low pressure UV-C:
-
effectively inactivates microorganisms
-
contributes to stable water quality
-
is energy-efficient and low-maintenance
In addition, these systems contribute to the reduction of monochloramine.
The limitation appears in the next stage. More complex chloramines — especially di- and trichloramine — are only broken down to a limited extent.
These compounds are exactly what cause:
-
the typical chlorine smell
-
irritation of the eyes and respiratory system
-
deterioration of indoor air quality
This is where the limits of low pressure UV-C become visible.
What Can Medium Pressure UV-C Systems Do — and What Can’t They Do?
Medium pressure systems operate with a much higher energy density and a broad spectrum of UV radiation.
This allows them to:
-
provide powerful, non-selective disinfection
-
effectively break down mono-, di- and trichloramines
-
initiate additional oxidative processes in the water
In practice, this means that medium pressure UV-C does more than disinfect. It actively contributes to improving overall water quality.
An important result of this is that:
-
chlorine odor decreases
-
indoor air quality improves
-
swimmer comfort increases significantly
At the same time, there are also considerations to keep in mind. Medium pressure systems generally have lower efficiency, a shorter lamp lifespan and higher energy consumption.
Chloramines: The Key to Making the Right Choice
To truly understand the difference, it is important to look at chloramines.
Chloramines are formed when chlorine reacts with organic contamination such as sweat and urine. This creates different forms:
-
monochloramine
-
dichloramine
-
trichloramine
Trichloramine in particular is responsible for the well-known “swimming pool smell.” This compound easily escapes from the water and concentrates just above the water surface — exactly where swimmers breathe.
-
Low pressure UV-C mainly affects monochloramine.
-
Medium pressure UV-C breaks down all forms.
This makes medium pressure UV-C a solution in many situations where low pressure systems cannot fully resolve the issue.
Application: Which System Should You Use and When?
The choice between low pressure and medium pressure strongly depends on the application.
In private swimming pools with a relatively low and predictable bather load, low pressure UV-C is often sufficient. It provides efficient disinfection with low operational costs.
However, that is not the full story.
Even in private pools, chlorine odor can become an issue — especially in:
-
indoor pools
-
spa-like environments
-
pools with more intensive use
In these situations, medium pressure UV-C can offer clear added value. By effectively breaking down trichloramine, the water becomes not only more hygienic, but also more pleasant to use.
In public swimming pools and wellness facilities, medium pressure UV-C is often the standard choice. Higher bather loads and more complex water balance conditions require a system that does more than simple disinfection.
The right choice therefore does not start with the lamp type, but with one simple question:
What problem does the system need to solve in the water?
