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How it Works: An Introduction to Vacuum Sewage and Plumbing Systems 

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A Vacuum Drainage System consists of three basic components

1. Collection Points – Typical sanitary and gray water collection points include toilets, sinks, showers, urinals, and drinking fountains. Typical condensate collection points consist of refrigeration coils, service coolers and freezers as well as frozen and refrigerated food display cases.

2. A Conveyance System – The vacuum drainage piping network can be routed where most convenient including overhead or through voids in ceiling spaces. This allows for transport of waste from its point of origin to the vacuum generating station.

3. Storage/Disposal Components – A vacuum generating station [Vac Center] includes the vacuum pumps that create a vacuum in the piping and storage tanks that collect and discharge the waste into the sewer system. The vacuum pumps run only on demand and redundancy is provided. The Vac Center may also include sewage discharge pumps that pump waste from the storage tanks into the sewer.

View the Vacuum Plumbing System Illustration

There are three primary components in a vacuum plumbing system

1. Vacuum Interface Valves and Intermediate Waste Collection Points

2. Conveyance System – The Vacuum Waste Piping Network

3. Vacuum Generating, Waste Collection and Disposal Components

Vacuum Interface Valves and Intermediate Waste Collection Points

The vacuum interface components allow waste to be introduced into the vacuum waste piping network and transported to the vacuum center. These components include a normally closed Extraction Valve, which separates the vacuum in the piping from atmospheric pressure surrounding the fixture, and a Controller, which operates the Extraction Valve.

The water closet Extraction Valve is connected to the waste outlet, separating the toilet from the piping network. When the flush valve is activated, the Controller opens the Extraction Valve, allowing atmospheric pressure at the toilet bowl to push waste to the waste outlet, through the Extraction Valve and into the waste piping. Because air is used to transport wastewater, no water is required to initiate the flush cycle. The Controller also activates the flush water valve for rinse and re-fill of the bowl. The opening and closing of the Extraction Valve is precisely controlled so that all waste is completely removed from the bowl.

Since only ½ gallon of water per flush is required, Acorn-Vac toilets provide a significant reduction in water use and sewage output. The reduced water requirement also allows water supply line sizing to be significantly smaller than that required for 1.28 or 1.6 gallon flush valves. In addition, conventional waste venting is not required.

In the case of urinals, flushing sinks and any other nonflushing fixture, the waste drainage process is similar, but typically includes the use of an intermediate waste collection point, or Accumulator. As waste drains from the fixture, it is temporarily collected at the Accumulator. As waste fills the Accumulator, a signal is detected by the Controller which opens the Extraction Valve. This causes air to enter the Accumulator, mixing with the waste and transporting the resultant emulsion into the piping network.

Conveyance System – The Vacuum Waste Piping Network

The vacuum waste piping or conveyance system is a closed piping network that is typically maintained under a continuous vacuum pressure of 16” – 18” Hg. (54 – 60 kPa) and is generally fabricated out of standard pressure rated PVC, Copper, or other smooth bore, non-porous material. The piping network consists of “risers” or “droppers” which transport the collected waste vertically from the point of origin to horizontal mains and branches leading to the Vac Center. Much like conventional waste piping, the mains and branches are typically installed with a slope of 1/4” per foot toward the Vac Center allowing the movement of waste to be assisted by gravity. However, unlike conventional waste piping, a continuous slope to the Vac Center does not need to be maintained. The vacuum waste piping network can be offset to recover grade, which allows the piping network to route horizontally over long distances in very shallow space. In addition, the vertical or horizontal piping can be easily offset to route around obstacles in its’ pathway toward the Vac Center. This feature can provide a significant benefit to the designer and installer when mechanical space is limited or when a conventional waste piping network can’t be readily accommodated or installed.

Vacuum Generating, Waste Collection and Disposal Components – The Vacuum Center

Commonly referred to as the “Vac Center”, the vacuum generating station includes vacuum pumps to create a continuous vacuum pressure within the piping network, and storage tanks that collect and discharge the waste into the facilities’ sewer main. In the case of sanitary waste, the Vac Center waste storage tanks are directly connected to sanitary sewer waste lines. Vacuum systems which provide drainage for greasy waste from food storage, display, or food preparation utility sinks are designed to allow for drainage from Vac Center waste collection tanks into code compliant grease interceptors, while vacuum systems processing condensate and grey water typically drain to a sanitary sewer through a code compliant air gap.

The vacuum waste piping network is directly connected to the Vac Center waste storage tanks. Waste travels under vacuum pressure from the fixture, through the piping network and into the Vac Center waste storage tanks, where it is temporarily held before discharge to sanitary waste lines or treatment equipment. Operation of the vacuum pumps and waste collection tanks is fully automated by controls provided with the Vac Center. The size of the vacuum pumps and waste collection tanks are determined by the total and potential future waste loads. In all cases, the Vac Center waste collection tanks and vacuum pumps are always selected and designed to provide redundant capacity.

The Vac Center controls automate the operation of the vacuum pumps which run only on demand as required to restore vacuum pressure to the waste collection tanks and piping network. Optional features allow remote visibility of the system operating status as well as visibility and control of individual valve operation.