Urinals are functioning correctly when they do not smell or become blocked. Waterless urinals perform just as well as flushed urinals, and usually a lot better, using a variety of methods.

Waterless Urinal Technologies

Microbiological Systems

• replaceable cartridges use the action of microbes to break down urine into odourless components and use the trap or u-bend as the seal against odour from the drains. 
• regular sluicing is required to prevent blockages.
• incompatible cleaning products should not be used, otherwise the system can be disabled, resulting in odours and blockages

• replaceable cartridges or in-built traps collect debris to help prevent blockages.  
• an oil-based sealant floats on top of the urine to prevent odours.  
• infrequent sluicing is recommended, usually when cartridge is changed or urinal serviced
• incompatible cleaning products and water may degrade the fluid seal, causing odours until the sealant is replaced

• replaceable cartridges or in-built traps have a one-way valve or siphon to prevent foul air from entering the washroom. 
• most models combine a single valve with a microbiological block to help break down urine and emit scent. The GW6 (illustrated) has a double skirt valve.
• regular sluicing or servicing is recommended to prevent blockages
• most, but not all, valve products are susceptible to damage by incompatible cleaning products. The latter should also not be used if a microbiological block forms part of the system.

How Flushed Urinals Work, by Comparison

Odour control: repeatedly reduce the number of odour-causing bacteria present by flushing them away. 

Blockage prevention: use a sudden flood of water to carry  hair and other debris down the waste pipes to the main drain. The more often they flush, the less likely potential obstructions are to remain in the pipes and cause a blockage. 

• Water contains limescale which combines with the salts in urine to form a hard scale that gradually blocks the waste pipes (see image right), 
• While urinals flushed every 5 minutes are unlikely to block, they are seldom allowed to do so because of the cost of water in money and environmental terms
• Flush controls that stop  flushing, especially when the washroom is not in use (e.g. overnight, weekends) accelerate the build-up of scale because urine and limescale has a respite from movement to  begin coating the pipes

Costs:

• Based on Gentworks survey data from hundreds of sites, the average annual water use per urinal is approximately 120 cubic metres (m³) per year. However, usage varies from around 29m³ to 235m³, depending on the level of flush control already implemented.
• Urinals with properly calibrated flush controllers will typically be using less than 50m³ per year. However most are flushing much more than expected because the controllers are not correctly calibrated or have failed completely.
• Urinals with correctly calibrated flush controllers using little water often suffer from more blockages. Therefore a natural response is to increase the water flow each time a blockage occurs.