UV Disinfection

UV disinfection works by exposing the water flow to high-intensity germicidal radiation inside a steel or technical polymer chamber. Ultraviolet light in the UV-C band, especially when concentrated at 254 nm, penetrates the cell walls of viruses, bacteria and cysts, irreversibly altering their DNA and preventing cell reproduction.

This process is purely physical and instantaneous, so it produces no residual by-products and does not alter the pool's pH. Since UV rays act only inside the reactor, it is essential to maintain a persistent chemical disinfectant baseline and periodically measure levels with a Lovibond MD200 3-in-1 Photometer for Chlorine, pH and Cyanuric Acid to ensure complete sterility in the pool.

UV disinfection drastically reduces chloramines, which cause strong odors and skin and mucous membrane irritation. That characteristic smell does not come from active free chlorine, but from the disinfectant combining with swimmers' organic matter.

UV-C radiation breaks down these combined chlorine bonds as the water passes through the reactor. By breaking down monochloramines and dichloramines, UV systems can reduce the need for oxidizing chlorine by up to 70%. Even so, to keep the pool sanitized against continuously introduced pathogens, you must maintain a baseline dose of products such as Quimiclor PS 5 Efectos Quimicamp 5 kg – 250 g Tablets (Multi-action Chlorine) at minimum maintenance levels.

No, UV disinfection does not completely replace chlorine or other chemical disinfectants with residual effects. The UV reactor performs large-scale physical sterilization inline, but its action stops immediately once the water leaves the unit and returns to the pool.

To prevent algae and pathogens from proliferating on the walls and bottom of the pool, a persistent residual agent is required. Combining UV radiation with automated dosing optimizes chemical consumption:

• Eliminates the need for recurring chlorine shock treatments.
• Stabilizes the free residual chlorine concentration at low levels of 0.5 to 1.0 ppm.
• Dramatically reduces oxidative wear on hydraulic components.
• Enables continuous automation using specialized equipment such as a Tekna AKS 603 Standard NHP Dosing Pump to maintain the exact balance.

A UV radiation system should always be installed on the pipe’s return line, after the sand or glass filter and before any heating or chemical dosing system. This setup ensures that water enters with minimal turbidity, optimizing the transmittance of germicidal rays.

For systems connected to pump sets commonly used in residential pools, installation must be carried out on a bypass with three ball valves:

• Allows you to calibrate the exact flow rate through the chamber according to the lamp’s wattage.
• Ensures the contact time needed to deliver the calculated lethal germicidal dose in mJ/cm2.
• Makes it easier to carry out routine maintenance or replace the quartz tube without stopping the pool’s overall flow.

Maintenance of an ultraviolet system focuses on replacing the germicidal lamp and cleaning the quartz sleeve. The UV-C lamp has an estimated optimal output lifespan of 9,000 to 12,000 hours of continuous operation; although it may continue emitting bluish visible light, its effective germicidal radiation decreases significantly after this period.

The protective quartz tube should also be inspected annually. If the water has high calcium hardness, limescale deposits build up on the glass and block UV-C radiation from reaching the water flow. Periodic cleaning with a mild acid descaler fully restores transparency and ensures the intended germicidal dose.

To select the right UV disinfection power, calculate the maximum flow rate supplied by the recirculation pump and compare it with the pool’s total volume. The system’s biocidal effectiveness depends strictly on the absorbed irradiation dose, which decreases if the water passes through the reactor too quickly.

In residential pools up to 40 or 50 m3, with pumping flow rates of 7 to 11 m3/h, 40 to 55 W lamps provide the required germicidal fluence of 30 mJ/cm2. If the flow rate exceeds the manufacturer’s stated technical capacity for the model, the water will not receive the exposure time needed to inactivate resistant pathogens.

UV disinfection reactors designed with a technical polymer or AISI-316L stainless steel chamber can withstand salt corrosion as long as the salinity does not exceed the manufacturer’s specifications. In salt-chlorinated installations with salt concentrations above 5 g/l, reactors with a polyethylene or titanium body are essential to prevent pitting caused by electrochemical corrosion.

In addition, the combination of UV radiation and salt electrolysis is highly synergistic. The lamp eliminates chloramines, which take the salt chlorinator longer to break down, allowing the cell’s output to be set to lower percentages. This extends the service life of the titanium electrodes and ensures notably lower electricity consumption.