Advantages and applications
Vacuum toilets require only one litre of water per flush compared with conventional toilets that use between 6 and 10 litres per flush, saving significant quantities of water. The volume of water required for urinals can also be reduced considerably and wash hand-basins can be fitted with tap aerators.
Vacuum sanitation technology is therefore used in buildings and at locations where large savings in water use are either required or can be generated. Ideal developments for vacuum installations are where there is a high density of sanitation fittings required or where the frequency of use is high, thus a lot of water can be saved.
Vacuum sanitation systems offer enormous flexibility for the pipe layout during both planning and installation. Main lines may be installed between suspended floors and ceilings. This gives the possibility of connecting sanitation fittings from above and from lower levels to only one single collection pipe. Pipelines do not need to be laid to a slope and are independent of natural falls. In addition to new buildings, ideal applications for vacuum technology are where the sanitation systems of old buildings are to be renewed.
The technical principles
Unlike conventional sanitation systems the pipe network in a vacuum system is constantly under negative pressure and therefore there is no leakage of wastewater.
A central vacuum station, comprising vacuum pumps, collection vessel, discharge pumps and associated controls etc, is generally located in the cellar of a building. The various sanitation fittings are each connected to the system via a vacuum valve. Each valve can be activated either by pushing a button or opens automatically.
The differential pressure across the valve evacuates the wastewater and the vacuum valve automatically closes after a few seconds. All wastewater is conveyed to the vacuum station collection vessel from where it is pumped in batches to the next public sewer line.
Vacuum sanitation systems can be built for blackwater (toilets) only or for the collection of greywater (washbasins, showers) and blackwater together or in separate pipes.