We have already written in the past about water dispensers and the risks associated with bacterial contamination. This is a serious issue that cannot be addressed with a purely commercial approach. Technical design and proper system management are essential. Water contamination can occur in three main ways: through the filtration system, from the dispensing point itself due to back-contamination, from non-sealed areas exposed to the external environment. Technical choices and material quality are the foundation for defining correct management protocols, routine maintenance, and, when necessary, extraordinary sanitation procedures.
In this article, we focus on one very specific critical point: the water dispensing spout
Debunking a Myth: Bacterial Sterilization at the Dispensing Point
Sterilizing water at the moment it passes through the dispensing spout is not possible. Small UV bactericidal systems installed directly at the outlet can never deliver a sufficient dose to guarantee complete water sterilization. Most of these systems are developed using UVC LED technology, mainly due to space constraints and the absence of hysteresis (the delay between lamp ignition and UVC emission). In some cases, they are marketed as a “healthy touch” solution. Serious manufacturers have managed to achieve doses of around 10,000 microwatt/cm², which is already a good level but still far from sufficient to guarantee the absence of bacterial load. The NSF/ANSI standards require much higher values
Moreover, these devices—while partially effective—face significant limitations: they cannot be used with carbonated water, as this would cause continuous dripping; when used with hot water, rapid surface clouding occurs, drastically reducing UV transmittance and therefore effectiveness.
UVC LED systems make sense only as protection of the dispensing point, acting as a sentinel against back-contamination, not as true water sterilizers.
UV Lamp at the spout
The use of quartz tube systems—where water flows inside a quartz tube irradiated by an external UV source—has strong emotional appeal but limited real effectiveness. Back in 2005, we developed several prototypes of such systems and even filed a patent. Traditional mercury vapor UVC lamps generate heat and must remain continuously switched on to function properly. The quartz tube—whether U-shaped or coiled—retains a volume of water that gradually heats up. Switching the lamp on only during dispensing is not a serious solution, as it eliminates the firewall function. As already mentioned, carbonated water cannot flow through these systems, as CO₂ residues would remain and contaminate subsequent dispensing. Finally, maintenance is a major issue: quartz tubes tend to become opaque over time, and cleaning them is far from easy. To maintain adequate UV transmittance, the tube must be replaced every 6 to 12 months.
Ozone: The “miracle solution” that doesn’t exist
For many, ozone disinfection is presented as the ultimate solution to bacterial contamination in water dispensers. It is often marketed as a device installed directly on the dispensing outlet. Ozone is indeed an extremely effective oxidizing bactericidal agent, but at the same time it is highly toxic to human health. It is used in some municipal water treatment plants as a pre-filtration disinfectant. Mineral water producers also use it—somewhat cleverly—to eliminate unstable compounds and, incidentally, sterilize the water.
One advantage of ozone is that it rapidly decomposes and dissolves (2O₃ ⇋ 3O₂). Its decay time in water depends on temperature and pH. At 15°C and neutral pH (7), it takes about 30 minutes for the concentration to halve. At 20°C, it takes about 20 minutes. However, due to its strong oxidative power, ozone can generate unpleasant odors and tastes, which must then be removed using activated carbon filters.
Ozone and risk management
It is unclear how the risk of ozone exposure is managed in treated drinking water dispensers, given its high toxicity and difficult handling. Despite this, ozone is widely used as a marketing claim. Imagine a dispensing spout periodically sprayed with ozone in bactericidal quantities: how is the end user protected from residual ozone? How is the correct dosage calculated? How is the surrounding air protected? For some, adding just a few nanograms (ppb) is enough to claim “Super Ozone Sterilization” on the product label…
Often, the real solution is to do almost nothing: a bit of light, a faint smell, and the product sells.
To conclude the topic of ozone, we would like to point out that in order to be placed on the market, it must comply with ECHA regulations, and in particular Regulation 528/20212.
Hollow fiber membranes: A partial solution
Hollow fiber membranes have pore sizes smaller than even the smallest bacteria. Today, membranes with porosities between 0.15 microns and 0.01 microns are commercially available at reasonable costs.
They provide a safe mechanical antibacterial barrier, but only for still and cold water. They cannot be used with carbonated or hot water.
When applied at the dispensing point for antibacterial purposes, hollow fiber membranes tend to reduce the quality and carbonation (perlage) of sparkling water. Additionally, their internal volume retains a certain amount of carbonated water, leading to several operational issues—especially if one attempts to use the same membrane for all three water types.
Beyond marketing gimmicks: The correct approach to reducing bacterial load at the dispensing point
We will never stop repeating it: reducing bacterial risk at the water outlet requires action on multiple fronts.
- High-quality design, minimizing areas where water can stagnate.
- Anti back-contamination devices at the outlet: UVC does not sterilize water during dispensing, but prevents bacterial ingress from the external environment.
- Material quality: the new regulations on materials in contact with drinking water require product validation tests to limit microbiological growth (Article 9, point C of Legislative Decree 102/2025).
- Proper routine maintenance, with clear protocols defining sanitizing agents, dosage, contact time, and minimum frequency.
- Technical staff training: how to operate, which criteria to follow, and which objectives to achieve.
- Daily system operation management: for example, removing the aerator and sanitizing it with hydrogen peroxide. It is no coincidence that microbiological water sampling standards require aerator removal, sanitation, and reinstallation before sampling.
- High-quality filtration systems: and yes, using ionic silver-treated filters helps stabilize the entire downstream system.
