DRAINAGE
Above: The Lowen unit at the Royal Cornwall Hospital in Truro features a day assessment area.
Above right:. The Haematology and Oncology Ward in the Royal Cornwall Hospital utilises vacuum drainage.
n Do not accept a traditional gravity drainage design featuring manholes located within the building fabric, and challenge the building design team to modify the design to incorporate only manholes located externally.
n Extend the project brief to include a formal appraisal of vacuum drainage systems. This is not a new, unproven technology, and should not be categorised as such.
Accepting that we all have a rudimentary understanding of what a traditional gravity system involves, what does a vacuum drainage system look like?
Example of vacuum drainage schematic (part) showing high level collection pipework routed to central core area, with zonal isolation valves.
Vacuum drainage systems A vacuum drainage system is a modern approach to managing building wastewater by utilising ‘negative’ pressure (vacuum) to transport fluids from a point of use – typically WCs, basins etc – to the local infrastructure drainage. Vacuum drainage can be viewed as the reverse of a cold water distribution system. Whereas cold water systems use positive pressure to distribute clean water from a central plant to points of use, vacuum drainage uses ‘negative’ pressure to collect wastewater from those same points and transport it to a central vacuum station. Unlike traditional drainage systems that rely on gravity and pipe slope to move fluids around the system, vacuum systems create a pressure difference that enhances efficiency and allows for greater flexibility in pipework location and route design.
Key components of a vacuum drainage system include:
n Vacuum Pump: this is the heart of the system, responsible for creating and maintaining the vacuum within the various collection pipes. Typically, vacuum pumps are arranged in pairs which comprise a unit with each pump providing 50 per cent of the duty; most pump units have a footprint size of 1200mm x 800mm and multiple pump units can be connected to provide the desired installation resilience (n+1) etc. The vacuum pump is best located within the building envelope at the lowest point of the pipe network.
n Vacuum collection pipes: pipe material can be either plastic or metal, transporting the waste from the appliance to the pump unit. A unique feature of a vacuum system is that the vertical connectivity of the pipework between floors is not sacrosanct. The pipework plan location can vary floor by floor without detriment to the system performance or increasing the possibility of blockages; hence this increases the pipe routing options exponentially and reflects the immense flexibility of the system, not confining sanitation service to predefined locations at an early design stage, making operational reconfiguration of the system more able to respond to operational changes without major structural intervention during the building’s life. The pipework layout flexibility has the additional advantage of allowing areas with a similar infection risk being connected to a common pipe network and those with different risk profiles can be segregated and kept apart therefore controlling the possibility of cross contamination between different patient groups or activities.
n Vacuum Interface unit: these include valves which allow the connection of any conventional sanitary appliance (basins, sinks, showers etc) to connect to a vacuum pipe network.
n Vacuum WCs: these are manufacturer specific sanitaryware items which are available in numerous design options covering both floor and wall mounted options. While of the same appearance as traditional WCs, vacuum toilets minimise water use (typically less than 1 litre per flush) and connect directly to the vacuum pipe network.
82 Health Estate Journal October 2026
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