Arros 9 fits smaller homes, Arros 15 is the mainstream larger-home option, and Arros 22 is for high-flow residential/light-commercial demand. Choose from validated flow at the dose target, not the model number alone.
Arros 9
VIQUA lists 9 GPM at 30 mJ/cm², 7 GPM at 40 mJ/cm² and 33W power consumption.
Arros 15
The 15 model is rated 15 GPM at 30 mJ/cm², 12 GPM at 40 mJ/cm² and 46W power consumption.
Arros 22
The largest model is rated 22 GPM at 30 mJ/cm², 16 GPM at 40 mJ/cm² and 60W power consumption.
Who should move up a size
Large showers, simultaneous fixture use, future additions or a calculated peak close to the smaller system limit are all reasons to choose the next flow tier.
How to size and install VIQUA Arros 9 vs 15 vs 22: Which UV System Size?
Equipment performance depends on matching capacity to the load rather than choosing the largest model. For pumps and heaters, that means required flow, pressure or temperature rise. For dehumidifiers and pool equipment, it means the environmental or hydraulic load. For UV treatment, it means validated flow at the required dose with appropriate upstream water quality.
Check electrical service, drainage, plumbing connections, clearance and ambient operating limits before purchase. A system can look ideal on a specification table but become expensive when the installation requires a new circuit, condensate pump, larger plumbing, structural changes or professional labor that was not included in the hardware price.
Operating cost, maintenance and failure points
Compare energy use and consumables over several years. Pumps, heaters, dehumidifiers and UV systems add electricity cost; pool and spa equipment may add filter or chemical maintenance; leak-detection devices may require batteries, valves or hub hardware. A lower purchase price can lose its advantage when operating cost or replacement parts are materially higher.
Look for serviceable components, warranty terms, replacement-part availability and the maintenance tasks the owner will actually perform. Equipment that depends on inaccessible proprietary parts or frequent neglected maintenance carries more long-term risk than a slightly more expensive system with clear service support.
Research basis
What to verify before acting on this guide
For VIQUA Arros 9 vs 15 vs 22: Which UV System Size?, the central question is whether the equipment is correctly sized for the actual load. Pumps and heaters depend on flow, pressure or temperature rise; dehumidifiers depend on moisture load and space conditions; pool equipment depends on hydraulic demand; UV systems depend on validated dose at a specified flow and upstream water quality. The largest model is not automatically the best fit.
Check installation requirements before comparing purchase prices. Electrical service, dedicated circuits, plumbing size, drain or condensate routing, clearances and ambient operating limits can add more cost than the hardware difference between two models. A specification that looks ideal can become impractical if the building cannot support it without substantial modification.
Long-term ownership and fit
Long-term ownership includes electricity, filters, lamps, chemicals, batteries, service parts and maintenance labor. Prefer equipment with clear replacement-part availability and maintenance tasks the owner is realistically likely to perform. Serviceability and support can be worth more than a small efficiency or price advantage.
VIQUA Arros 9 vs 15 vs 22 should be chosen from validated flow at the required UV dose
UV sizing is not just a bathroom-count exercise. The reactor must deliver the required UV dose at the household’s peak flow and under the water-quality conditions specified by the manufacturer. Start with realistic simultaneous demand, then compare the validated flow rating for Arros 9, 15 and 22 rather than simply buying the largest chamber. Oversizing increases cost, while undersizing risks pushing water through faster than the validated treatment rate.
Pretreatment matters equally. Turbidity, iron, manganese and hardness scale can reduce UV transmission or foul the quartz sleeve, so filtration and conditioning often belong upstream. Verify electrical requirements, lamp or module replacement cost, sleeve maintenance and available installation space. Choose the smallest Arros model whose validated flow comfortably exceeds the actual peak demand after pretreatment conditions are met. That gives better value than sizing from headline flow alone.