There is a perception among many people that flush-type public urinals are automatically more hygienic and result in less odor problems than waterless public urinals.
It is interesting though to note, though, just how many flush-type public urinals contain antibacterial deodorizing blocks or cakes (sometimes also called urinal pucks). If this type of urinal did a really good job of controlling the multiplication and spread of bacteria with the resultant odor problems, then why are these extra control measures necessary?
In some establishments, you will even see ice in urinals. The theory behind this practice is that bacteria need a warm, moist environment in order to multiply and cause odors, so cooling down the environment will limit the bacterial activity in these public urinals.
The problem with this approach is that it only half solves the problem – cooling the bacteria and washing them out of the urinal bowl does not solve the problem – it merely moves it deeper into the system. Sooner or later, these bacteria will reach a moist, warm place deeper in the system, and problems are sure to result as their activity becomes concentrated deeper in the plumbing system.
Waterless urinals solve the problem by making sure the urinal bowl area is dry and therefore an inhospitable environment for bacteria. Most odor-causing bacteria will simply die in the urinal, and those that survive will become trapped in or below the cartridge, where they will die due to lack of oxygen in that part of the system.