Water is used in conventional urinals to wash the bowl and flush the trap. In practice ceramic urinals repel urine and remain surprisingly fresh without flushing.
Similarly standard UK urinals do not actually flush the trap in the way that a WC is flushed but instead just dilute the urine without removing solids such as hair, scale and cigarette ends. As a result, even 'flushing' urinals tend to block and in hard-water areas tough scale will build up quickly in traps and pipes.
How much water can they save?
The Water Regulations specify a maximum water usage of 7.5 litres per urinal bowl, or 700mm of slab, per hour (10 litres for a single bowl). A device must be fitted to prevent the urinals flushing when the building is unoccupied.
Assuming correct adjustment this means that each bowl uses about 27 m3/year for a public toilet open for 10 hours every day. An uncontrolled urinal, but still adjusted to the correct rate would use over 60m3/year. In practice flushing rates are usually much higher.
However water saving is not the only reason to specify waterless urinals as they promise a range of benefits including:
Reduced water and sewage charges (where relevant).
Reduced pipe blockage in hard water areas.
Avoidance of odorous lime-scale on urinal bowls.
Reduced sewage volumes to soakaways and treatment plants.
Immunity to frost.
Less temptation for vandals.
No flooding of rooms when traps block or are deliberately blocked.
No flush controllers to maintain or fail.
Lower installation costs.
If all these promises can be met, then waterless urinals should offer benefits even where water is free of charge and in abundant supply.
In practice a number of issues have tempered enthusiasm for waterless urinals, namely:
The cost of consumables may exceed the cost of the water saved.
The environmental cost of consumables may outweigh the environmental benefit of reduced water use (chemicals, waste to landfill, plastics).
Many systems require regular and correct maintenance to prevent odour and blockage, or require a maintenance contract making them uneconomic for smaller installations.
Standard urinal problems such as leakage and splashing, which lead to odour, are not addressed by most designs.
Any odour or blockage will be assumed to be due to waterless operation whereas odour or blockage in conventional urinals is not attributed to the technology.
How do waterless urinals work?
The two main issues that must be addressed for any urinal installation are odour and blockage. Simply turning off the water to standard urinals should not lead to odour. In fact the lack of lime-scale on the urinal surface can reduce smell. While the stale urine in urinal traps is extremely malodorous, this smell does not normally escape into the room, unless of course the trap is leaking onto the floor. This is perhaps less surprising when sink and basin traps are considered. If these are dismantled the resulting rancid smell is extremely unpleasant and yet we wash our faces and dishes in close proximity without the need for lemon-fresh sink plugs.
Despite research indicating the lack of odour from un-flushed urinal bowls, most commercial waterless systems incorporate anti-odour measures such as scented pads, sticks, blocks or mats. These scents may be useful for masking general toilet smells but there is little evidence for their need to mask smells from the actual urinal bowl or trap. Some of the scented sticks and blocks are claimed to have anti-scale properties, some are 'biological', containing enzymes whilst others contain disinfectants. In hard-water areas, turning off the water may reduce scale build-up but traps will still block as salts and solids accumulate. The solution is to pour about 2 litres of warm water (perhaps with detergent) down the urinal typically once a week.
The AIRFLUSH® Waterless Urinal System addresses all of the common problems normally associated with waterless urinals. The System offers waterless operation without any of the consumables normally associated with this type of system. Please click here for more information.
