Ventilation Systems

Ventilation header
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A drainage pipe is normally at neutral air pressure compared to the surrounding atmosphere. When a column of wastewater flows through a pipe, it compresses air in the pipe, creating a positive pressure that must be released or it will push back on the waste stream and downstream traps’ water seals. As the column of water passes, air must flow in behind the waste stream or negative pressure (suction) results. The extent of these pressure fluctuations is determined by the waste discharge fluid volume.

The purpose of a ventilation stack is to control pressure in the pipework to prevent foul air from the wastewater system entering the building. Below are some of the main configuration principles, but combinations and variations are often required (see standard EN 12056-2). The purpose of a ventilation stack is also to avoid accumulation of dangerous gases.

Black water and grey water can be drained either in separate or in a single discharge stack. The rules for duct sizing are different depending on the option selected.

Primary ventilated system configurations

Control of pressure is achieved by air fl ow in the discharge stacks. The soil stacks extend in main roof vents to above and out of the roof. Alternatively, air admittance valves may be used. They are pressure-activated, one-way mechanical vents, used in a plumbing system to eliminate the need for conventional pipe venting and roof penetrations.

A single stack is still possible but design precautions must be taken to prevent self-siphonage.

Primary ventilated system configurations

Control of pressure is achieved by air fl ow in the discharge stacks. The soil stacks extend in main roof vents to above and out of the roof. Alternatively, air admittance valves may be used. They are pressure-activated, one-way mechanical vents, used in a plumbing system to eliminate the need for conventional pipe venting and roof penetrations.

A single stack is still possible but design precautions must be taken to prevent self-siphonage.

Secondary ventilated system configurations

In buildings of three or more storeys, if the air pressure within the stack suddenly becomes higher than ambient, this positive transient could cause wastewater to be pushed into the fi xture, breaking the trap seal. Vent stacks are put in parallel to waste stacks to allow proper venting and prevent such disorders. Air admittance valves may also be used in this confi guration. Under many building codes, a vent stack, a pipe leading to the main roof vent, is required to the draining fi xtures (sink, toilet, shower stall, etc.).

To allow only one vent stack and therefore one roof penetration, as permitted by local building codes, sub-vents may be tied together and exit a common vent stack.

Secondary ventilated system configurations

In buildings of three or more storeys, if the air pressure within the stack suddenly becomes higher than ambient, this positive transient could cause wastewater to be pushed into the fi xture, breaking the trap seal. Vent stacks are put in parallel to waste stacks to allow proper venting and prevent such disorders. Air admittance valves may also be used in this confi guration. Under many building codes, a vent stack, a pipe leading to the main roof vent, is required to the draining fi xtures (sink, toilet, shower stall, etc.).

To allow only one vent stack and therefore one roof penetration, as permitted by local building codes, sub-vents may be tied together and exit a common vent stack.

SINGLE STACK BRANCH

The single stack branch is a patented device made to allow wastewater drainage without secondary vent pipes.

Single Stack Branch SMU S, 3D image             Field of use

 


Benefits

It simplifies plumbing by grouping pipework from 3 or 4 times more sources than a conventional installation.

The single stack branch is particularly suitable for narrow service shafts, hotel rooms, student apartments or any other buildings with adjacent sanitary blocks.

  • Multi-connection of sanitary appliances for adjacent apartments, or sanitary blocks
  • Compactness when space is limited
  • No secondary vent pipes are required.

 

Solution

The single stack branch exists as a long tail to allow connection to the main stack under the slab and thus facilitate installation either in new or renovation works.

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