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The soil and waste drainage piping system is a critical component of any plumbing system in a building. It is responsible for carrying waste and soil from the fixtures to the main sewer line or septic tank.

• The Piping system to be adopted will depend on the type and planning of the building in which it is to be installed and will be one of the following.

1. Single stack system
2. One pipe (Partially ventilated system)
3. One pipe (Fully ventilated system)
4. Two pipe system

1) Single stack system

• The piping system in which there is no trap ventilation and the stack itself acts as vent through roof.
• In this system care shall be taken for proper sizing of the pipes and the trap arm distance, specially the horizontal distance of sanitary fixtures from the drainage stack and vertical distance between connection of branches from fixtures to drainage stack.

2) One pipe (Partially ventilated system)

• The piping system in which soil and waste pipes are connected to a single vertical stack [ as explained in Single stack system ] with additional vent pipe for ventilation of traps of water closets.
• It is also sometimes known as single stack partially ventilated system.

3) One pipe (Fully ventilated system)

• The piping system in which the waste pipes from the sinks, baths and wash basins, and the soil pipe from water closet are connected to a single vertical stack.
• The traps of the water closets, waste appliances, etc, are individually ventilated and connected with a separate stack to preserve the water seal.
• It is also sometimes known as single stack fully ventilated system.

4) Two pipe system

i) Two pipe system with common vent pipe

• The piping system in which all soil appliances such as water closets, urinals, bidet and bedpan sinks are connected to soil stack and all other plumbing fixtures such as baths, sinks, and basins are connected to waste stack through deep seal trap.
• In addition, a common vent stack is provided for ventilation of soil and waste stacks.

ii) Two pipe system with independent vent pipes

• The piping system in which all soil appliances such as water closets, urinals , bidet and bedpan sinks are connected to soil stack, and all other plumbing fixtures such as baths, sinks, and basins are connected to waste stack through deep seal trap.
• In addition, there are independent a vent stacks provided for respective ventilation of soil and waste stacks.

The soil and waste piping system must be properly installed and maintained to ensure that it functions properly and to prevent blockages, leaks, and backups. It’s essential to follow local codes and regulations when installing a soil and waste drainage system, as well as to hire a licensed plumber to do the work if you are not familiar with plumbing systems.

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